Method and apparatus for detection of multiple analytes

ABSTRACT

An apparatus for analyzing the composition of bodily fluid. The apparatus comprises a fluid handling network including a patient end configured to maintain fluid communication with a bodily fluid in a patient and at least one pump intermittently operable to draw a sample of bodily fluid from the patient. The apparatus further comprises a fluid analyzer positioned to analyze at least a portion of the sample and measure the presence of two or more analytes. Also disclosed is a method for analyzing the composition of a bodily fluid in a patient. The method comprises drawing a sample of the bodily fluid of the patient through a fluid handling network configured to maintain fluid communication with a bodily fluid in a patient. The method further comprises analyzing the at least a portion of the sample in a fluid analyzer to estimate the concentration of two or more analytes in the sample.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 60/652,660, filed Feb. 14, 2005, titledANALYTE DETECTION SYSTEM; U.S. Provisional Application No. 60/658,001,filed Mar. 2, 2005, titled SEPARATING BLOOD SAMPLE FOR ANALYTE DETECTIONSYSTEM; U.S. Provisional Application No. 60/673,551, filed Apr. 21,2005, titled APPARATUS AND METHODS FOR SEPARATING SAMPLE FOR ANALYTEDETECTION SYSTEM; and of U.S. Provisional Application No. 60/724,199,filed Oct. 6, 2005, titled INTENSIVE CARE UNIT BLOOD ANALYSIS SYSTEM ANDMETHOD. The entire contents of each of the above-listed provisionalapplications are hereby incorporated by reference herein and made partof this specification.

BACKGROUND

1. Field

Certain embodiments disclosed herein relate to methods and apparatus fordetermining the concentration of an analyte in a sample, such as ananalyte in a sample of bodily fluid, as well as methods and apparatuswhich can be used to support the making of such determinations.

2. Description of the Related Art

It is a common practice to measure the levels of certain analytes, suchas glucose, in a bodily fluid, such as blood. Often this is done in ahospital or clinical setting when there is a risk that the levels ofcertain analytes may move outside a desired range, which in turn canjeopardize the health of a patient. Certain currently known systems foranalyte monitoring in a hospital or clinical setting suffer from variousdrawbacks.

SUMMARY

One disclosed embodiment comprises an apparatus for analyzing thecomposition of bodily fluid. The apparatus comprises a fluid handlingnetwork including a patient end configured to maintain fluidcommunication with a bodily fluid in a patient and at least one pumpintermittently operable to draw a sample of bodily fluid from thepatient. The apparatus further comprises a fluid analyzer positioned toanalyze at least a portion of the sample and measure the presence of twoor more analytes.

Another disclosed embodiment comprises a method for analyzing thecomposition of a bodily fluid in a patient. The method comprises drawinga sample of the bodily fluid of the patient through a fluid handlingnetwork configured to maintain fluid communication with a bodily fluidin a patient. The method further comprises analyzing the at least aportion of the sample in a fluid analyzer to estimate the concentrationof two or more analytes in the sample.

Another disclosed embodiment comprises an apparatus for analyzing thecomposition of bodily fluid. The apparatus comprises means for drawing asample of the bodily fluid of the patient through a fluid handlingnetwork configured to maintain fluid communication with a bodily fluidin a patient; and means for analyzing the at least a portion of thesample in a fluid analyzer to estimate the concentration of two or moreanalytes in the sample.

Certain objects and advantages of the invention(s) are described herein.Of course, it is to be understood that not necessarily all such objectsor advantages may be achieved in accordance with any particularembodiment. Thus, for example, those skilled in the art will recognizethat the invention(s) may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other objects or advantages as maybe taught or suggested herein.

Certain embodiments are summarized above. However, despite the foregoingdiscussion of certain embodiments, only the appended claims (and not thepresent summary) are intended to define the invention(s). The summarizedembodiments, and other embodiments, will become readily apparent tothose skilled in the art from the following detailed description of thepreferred embodiments having reference to the attached figures, theinvention(s) not being limited to any particular embodiment(s)disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a fluid handling system in accordance with oneembodiment;

FIG. 1A is a schematic of a fluid handling system, wherein a fluidhandling and analysis apparatus of the fluid handling system is shown ina cutaway view;

FIG. 1B is a cross-sectional view of a bundle of the fluid handlingsystem of FIG. 1A taken along the line 1B-1B;

FIG. 2 is a schematic of an embodiment of a sampling apparatus of thepresent invention;

FIG. 3 is a schematic showing details of an embodiment of a samplingapparatus of the present invention;

FIG. 4 is a schematic of an embodiment of a sampling unit of the presentinvention;

FIG. 5 is a schematic of an embodiment of a sampling apparatus of thepresent invention;

FIG. 6A is a schematic of an embodiment of gas injector manifold of thepresent invention;

FIG. 6B is a schematic of an embodiment of gas injector manifold of thepresent invention;

FIGS. 7A-7J are schematics illustrating methods of using the infusionand blood analysis system of the present invention, where FIG. 7A showsone embodiment of a method of infusing a patient, and FIGS. 7B-7Jillustrate steps in a method of sampling from a patient, where FIG. 7Bshows fluid being cleared from a portion of the first and secondpassageways; FIG. 7C shows a sample being drawn into the firstpassageway; FIG. 7D shows a sample being drawn into second passageway;FIG. 7E shows air being injected into the sample; FIG. 7F shows bubblesbeing cleared from the second passageway; FIGS. 7H and 7I show thesample being pushed part way into the second passageway followed byfluid and more bubbles; and FIG. 7J shows the sample being pushed toanalyzer;

FIG. 8 is a perspective front view of an embodiment of a samplingapparatus of the present invention;

FIG. 9 is a schematic front view of one embodiment of a samplingapparatus cassette of the present invention;

FIG. 10 is a schematic front view of one embodiment of a samplingapparatus instrument of the present invention;

FIG. 11 is an illustration of one embodiment of an arterial patientconnection of the present invention;

FIG. 12 is an illustration of one embodiment of a venous patientconnection of the present invention;

FIGS. 13A, 13B, and 13C are various views of one embodiment of a pinchvalve of the present invention, where FIG. 13A is a front view, FIG. 13Bis a sectional view, and FIG. 13C is a sectional view showing one valvein a closed position;

FIGS. 14A and 14B are various views of one embodiment of a pinch valveof the present invention, where FIG. 14A is a front view and FIG. 14B isa sectional view showing one valve in a closed position;

FIG. 15 is a side view of one embodiment of a separator;

FIG. 16 is an exploded perspective view of the separator of FIG. 15;

FIG. 17 is one embodiment of a fluid analysis apparatus of the presentinvention;

FIG. 18 is a top view of a cuvette for use in the apparatus of FIG. 17;

FIG. 19 is a side view of the cuvette of FIG. 18;

FIG. 20 is an exploded perspective view of the cuvette of FIG. 18;

FIG. 21 is a schematic of an embodiment of a sample preparation unit;

FIG. 22A is a perspective view of another embodiment of a fluid handlingand analysis apparatus having a main instrument and removable cassette;

FIG. 22B is a partial cutaway, side elevational view of the fluidhandling and analysis apparatus with the cassette spaced from the maininstrument;

FIG. 22C is a cross-sectional view of the fluid handling and analysisapparatus of FIG. 22A wherein the cassette is installed onto the maininstrument;

FIG. 23A is a cross-sectional view of the cassette of the fluid handlingand analysis apparatus of FIG. 22A taken along the line 23A-23A;

FIG. 23B is a cross-sectional view of the cassette of FIG. 23A takenalong the line 23B-23B of FIG. 23A;

FIG. 23C is a cross-sectional view of the fluid handling and analysisapparatus having a fluid handling network, wherein a rotor of thecassette is in a generally vertical orientation;

FIG. 23D is a cross-sectional view of the fluid handling and analysisapparatus, wherein the rotor of the cassette is in a generallyhorizontal orientation;

FIG. 23E is a front elevational view of the main instrument of the fluidhandling and analysis apparatus of FIG. 23C;

FIG. 24A is a cross-sectional view of the fluid handling and analysisapparatus having a fluid handling network in accordance with anotherembodiment;

FIG. 24B is a front elevational view of the main instrument of the fluidhandling and analysis apparatus of FIG. 24A;

FIG. 25A is a front elevational view of a rotor having a sample elementfor holding sample fluid;

FIG. 25B is a rear elevational view of the rotor of FIG. 25A;

FIG. 25C is a front elevational view of the rotor of FIG. 25A with thesample element filled with a sample fluid;

FIG. 25D is a front elevational view of the rotor of FIG. 25C after thesample fluid has been separated;

FIG. 25E is a cross-sectional view of the rotor taken along the line25E-25E of FIG. 25A;

FIG. 25F is an enlarged sectional view of the rotor of FIG. 25E;

FIG. 26A is an exploded perspective view of a sample element for usewith a rotor of a fluid handling and analysis apparatus;

FIG. 26B is a perspective view of an assembled sample element;

FIG. 27A is a front elevational view of a fluid interface for use with acassette;

FIG. 27B is a top elevational view of the fluid interface of FIG. 27A;

FIG. 27C is an enlarged side view of a fluid interface engaging a rotor;

FIG. 28 is a cross-sectional view of the main instrument of the fluidhandling and analysis apparatus of FIG. 22A taken along the line 28-28;

FIG. 29 is a graph illustrating the absorption spectra of variouscomponents that may be present in a blood sample;

FIG. 30 is a graph illustrating the change in the absorption spectra ofblood having the indicated additional components of FIG. 29 relative toa Sample Population blood and glucose concentration, where thecontribution due to water has been numerically subtracted from thespectra;

FIG. 31 is an embodiment of an analysis method for determining theconcentration of an analyte in the presence of possible interferents;

FIG. 32 is one embodiment of a method for identifying interferents in asample for use with the embodiment of FIG. 31;

FIG. 33A is a graph illustrating one embodiment of the method of FIG.32, and FIG. 33B is a graph further illustrating the method of FIG. 32;

FIG. 34 is a one embodiment of a method for generating a model foridentifying possible interferents in a sample for use with an embodimentof FIG. 31;

FIG. 35 is a schematic of one embodiment of a method for generatingrandomly-scaled interferent spectra;

FIG. 36 is one embodiment of a distribution of interferentconcentrations for use with the embodiment of FIG. 35;

FIG. 37 is a schematic of one embodiment of a method for generatingcombination interferent spectra;

FIG. 38 is a schematic of one embodiment of a method for generating aninterferent-enhanced spectral database;

FIG. 39 is a graph illustrating the effect of interferents on the errorof glucose estimation;

FIGS. 40A, 40B, 40C, and 40D each have a graph showing a comparison ofthe absorption spectrum of glucose with different interferents takenusing two different techniques: a Fourier Transform Infrared (FTIR)spectrometer having an interpolated resolution of 1 cm⁻¹ (solid lineswith triangles); and by 25 finite-bandwidth IR filters having a Gaussianprofile and full-width half-maximum (FWHM) bandwidth of 28 cm⁻¹corresponding to a bandwidth that varies from 140 nm at 7.08 μm, up to279 nm at 10 μm (dashed lines with circles). The Figures show acomparison of glucose with mannitol (FIG. 40A), dextran (FIG. 40B),n-acetyl L cysteine (FIG. 40C), and procainamide (FIG. 40D), at aconcentration level of 1 mg/dL and path length of 1 μm;

FIG. 41 shows a graph of the blood plasma spectra for 6 blood sampletaken from three donors in arbitrary units for a wavelength range from 7μm to 10 μm, where the symbols on the curves indicate the centralwavelengths of the 25 filters;

FIGS. 42A, 42B, 42C, and 42D contain spectra of the Sample Population of6 samples having random amounts of mannitol (FIG. 42A), dextran (FIG.42B), n-acetyl L cysteine (FIG. 42C), and procainamide (FIG. 42D), at aconcentration levels of 1 mg/dL and path lengths of 1 μm;

FIGS. 43A-43D are graphs comparing calibration vectors obtained bytraining in the presence of an interferent, to the calibration vectorobtained by training on clean plasma spectra for mannitol (FIG. 43A),dextran (FIG. 43B), n-acetyl L cysteine (FIG. 43C), and procainamide(FIG. 43D) for water-free spectra;

FIG. 44 is a schematic illustration of another embodiment of the analytedetection system;

FIG. 45 is a plan view of one embodiment of a filter wheel suitable foruse in the analyte detection system depicted in FIG. 44;

FIG. 46 is a partial sectional view of another embodiment of an analytedetection system;

FIG. 47 is a detailed sectional view of a sample detector of the analytedetection system illustrated in FIG. 46;

FIG. 48 is a detailed sectional view of a reference detector of theanalyte detection system illustrated in FIG. 46; and

FIG. 49 is a flowchart of a variation of the method shown in flowchartform in FIG. 31.

Reference symbols are used in the Figures to indicate certaincomponents, aspects or features shown therein, with reference symbolscommon to more than one Figure indicating like components, aspects orfeatures shown therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although certain preferred embodiments and examples are disclosed below,it will be understood by those skilled in the art that the inventivesubject matter extends beyond the specifically disclosed embodiments toother alternative embodiments and/or uses of the invention, and toobvious modifications and equivalents thereof. Thus it is intended thatthe scope of the inventions herein disclosed should not be limited bythe particular disclosed embodiments described below. Thus, for example,in any method or process disclosed herein, the acts or operations makingup the method/process may be performed in any suitable sequence, and arenot necessarily limited to any particular disclosed sequence. Forpurposes of contrasting various embodiments with the prior art, certainaspects and advantages of these embodiments are described whereappropriate herein. Of course, it is to be understood that notnecessarily all such aspects or advantages may be achieved in accordancewith any particular embodiment. Thus, for example, it should berecognized that the various embodiments may be carried out in a mannerthat achieves or optimizes one advantage or group of advantages astaught herein without necessarily achieving other aspects or advantagesas may be taught or suggested herein. While the systems and methodsdiscussed herein can be used for invasive techniques, the systems andmethods can also be used for non-invasive techniques or other suitabletechniques, and can be used in hospitals, healthcare facilities, ICUs,or residences.

Overview of Embodiments of Fluid Handling Systems

Disclosed herein are fluid handling systems and various methods ofanalyzing sample fluids. FIG. 1 illustrates an embodiment of a fluidhandling system 10 which can determine the concentration of one or moresubstances in a sample fluid, such as a whole blood sample from apatient P. The fluid handling system 10 can also deliver an infusionfluid 14 to the patient P.

The fluid handling system 10 is located bedside and generally comprisesa container 15 holding the infusion fluid 14 and a sampling system 100which is in communication with both the container 15 and the patient P.A tube 13 extends from the container 15 to the sampling system 100. Atube 12 extends from the sampling system 100 to the patient P. In someembodiments, one or more components of the fluid handling system 10 canbe located at another facility, room, or other suitable remote location.One or more components of the fluid handling system 10 can communicatewith one or more other components of the fluid handling system 10 (orwith other devices) by any suitable communication means, such ascommunication interfaces including, but not limited to, opticalinterfaces, electrical interfaces, and wireless interfaces. Theseinterfaces can be part of a local network, internet, wireless network,or other suitable networks.

The Infusion fluid 14 can comprise water, saline, dextrose, lactatedRinger's solution, drugs, insulin, mixtures thereof, or other suitablesubstances. The illustrated sampling system 100 allows the infusionfluid to pass to the patient P and/or uses the infusion fluid in theanalysis. In some embodiments, the fluid handling system 10 may notemploy infusion fluid. The fluid handling system 10 may thus drawsamples without delivering any fluid to the patient P.

The sampling system 100 can be removably or permanently coupled to thetube 13 and tube 12 via connectors 110, 120. The patient connector 110can selectively control the flow of fluid through a bundle 130, whichincludes a patient connection passageway 112 and a sampling passageway113, as shown in FIG. 1B. The sampling system 100 can also draw one ormore samples from the patient P by any suitable means. The samplingsystem 100 can perform one or more analyses on the sample, and thenreturns the sample to the patient or a waste container. In someembodiments, the sampling system 100 is a modular unit that can beremoved and replaced as desired. The sampling system 100 can include,but is not limited to, fluid handling and analysis apparatuses,connectors, passageways, catheters, tubing, fluid control elements,valves, pumps, fluid sensors, pressure sensors, temperature sensors,hematocrit sensors, hemoglobin sensors, colorimetric sensors, and gas(or “bubble”) sensors, fluid conditioning elements, gas injectors, gasfilters, blood plasma separators, and/or communication devices (e.g.,wireless devices) to permit the transfer of information within thesampling system or between sampling system 100 and a network. Theillustrated sampling system 100 has a patient connector 110 and a fluidhandling and analysis apparatus 140, which analyzes a sample drawn fromthe patient P. The fluid handling and analysis apparatus 140 and patientconnector 110 cooperate to control the flow of infusion fluid into,and/or samples withdrawn from, the patient P. Samples can also bewithdrawn and transferred in other suitable manners.

FIG. 1A is a close up view of the fluid handling and analysis apparatus140 which is partially cutaway to reveal some of its internalcomponents. The fluid handling and analysis apparatus 140 preferablyincludes a pump 203 that controls the flow of fluid from the container15 to the patient P and/or the flow of fluid drawn from the patient P.The pump 203 can selectively control fluid flow rates, direction(s) offluid flow(s), and other fluid flow parameters as desired. As usedherein, the term “pump” is a broad term and means, without limitation, apressurization/pressure device, vacuum device, or any other suitablemeans for causing fluid flow. The pump 203 can include, but is notlimited to, a reversible peristaltic pump, two unidirectional pumps thatwork in concert with valves to provide flow in two directions, aunidirectional pump, a displacement pump, a syringe, a diaphragm pump,roller pump, or other suitable pressurization device.

The illustrated fluid handling and analysis apparatus 140 has a display141 and input devices 143. The illustrated fluid handling and analysisapparatus 140 can also have a sampling unit 200 configured to analyzethe drawn fluid sample. The sampling unit 200 can thus receive a sample,prepare the sample, and/or subject the sample (prepared or unprepared)to one or more tests. The sampling unit 200 can then analyze resultsfrom the tests. The sampling unit 200 can include, but is not limitedto, separators, filters, centrifuges, sample elements, and/or detectionsystems, as described in detail below. The sampling unit 200 (see FIG.3) can include an analyte detection system for detecting theconcentration of one or more analytes in the body fluid sample. In someembodiments, the sampling unit 200 can prepare a sample for analysis. Ifthe fluid handling and analysis apparatus 140 performs an analysis onplasma contained in whole blood taken from the patient P, filters,separators, centrifuges, or other types of sample preparation devicescan be used to separate plasma from other components of the blood. Afterthe separation process, the sampling unit 200 can analyze the plasma todetermine, for example, the patient P's glucose level. The sampling unit200 can employ spectroscopic methods, calorimetric methods,electrochemical methods, or other suitable methods for analyzingsamples.

With continued reference to FIGS. 1 and 1A, the fluid 14 in thecontainer 15 can flow through the tube 13 and into a fluid sourcepassageway 111. The fluid can further flow through the passageway 111 tothe pump 203, which can pressurize the fluid. The fluid 14 can then flowfrom the pump 203 through the patient connection passageway 112 andcatheter 11 into the patient P. To analyze the patient's P body fluid(e.g., whole blood, blood plasma, interstitial fluid, bile, sweat,excretions, etc.), the fluid handling and analysis apparatus 140 candraw a sample from the patient P through the catheter 11 to a patientconnector 110. The patient connector 110 directs the fluid sample intothe sampling passageway 113 which leads to the sampling unit 200. Thesampling unit 200 can perform one or more analyses on the sample. Thefluid handling and analysis apparatus 140 can then output the resultsobtained by the sampling unit 200 on the display 141.

In some embodiments, the fluid handling system 10 can draw and analyzebody fluid sample(s) from the patient P to provide real-time ornear-real-time measurement of glucose levels. Body fluid samples can bedrawn from the patient P continuously, at regular intervals (e.g., every5, 10, 15, 20, 30 or 60 minutes), at irregular intervals, or at any timeor sequence for desired measurements. These measurements can bedisplayed bedside with the display 141 for convenient monitoring of thepatient P.

The illustrated fluid handling system 10 is mounted to a stand 16 andcan be used in hospitals, ICUs, residences, healthcare facilities, andthe like. In some embodiments, the fluid handling system 10 can betransportable or portable for an ambulatory patient. The ambulatoryfluid handling system 10 can be coupled (e.g., strapped, adhered, etc.)to a patient, and may be smaller than the bedside fluid handling system10 illustrated in FIG. 1. In some embodiments, the fluid handling system10 is an implantable system sized for subcutaneous implantation and canbe used for continuous monitoring. In some embodiments, the fluidhandling system 10 is miniaturized so that the entire fluid handlingsystem can be implanted. In other embodiments, only a portion of thefluid handling system 10 is sized for implantation.

In some embodiments, the fluid handling system 10 is a disposable fluidhandling system and/or has one or more disposable components. As usedherein, the term “disposable” when applied to a system or component (orcombination of components), such as a cassette or sample element, is abroad term and means, without limitation, that the component in questionis used a finite number of times and then discarded. Some disposablecomponents are used only once and then discarded. Other disposablecomponents are used more than once and then discarded. For example, thefluid handling and analysis apparatus 140 can have a main instrument anda disposable cassette that can be installed onto the main instrument, asdiscussed below. The disposable cassette can be used for predeterminedlength of time, to prepare a predetermined amount of sample fluid foranalysis, etc. In some embodiments, the cassette can be used to preparea plurality of samples for subsequent analyses by the main instrument.The reusable main instrument can be used with any number of cassettes asdesired. Additionally or alternatively, the cassette can be a portable,handheld cassette for convenient transport. In these embodiments, thecassette can be manually mounted to or removed from the main instrument.In some embodiments, the cassette may be a non disposable cassette whichcan be permanently coupled to the main instrument, as discussed below.

Disclosed herein are a number of embodiments of fluid handling systems,sampling systems, fluid handling and analysis apparatuses, analytedetection systems, and methods of using the same. Section I belowdiscloses various embodiments of the fluid handling system that may beused to transport fluid from a patient for analysis. Section II belowdiscloses several embodiments of fluid handling methods that may be usedwith the apparatus discussed in Section I. Section III below disclosesseveral embodiments of a sampling system that may be used with theapparatus of Section I or the methods of Section II. Section IV belowdiscloses various embodiments of a sample analysis system that may beused to detect the concentration of one or more analytes in a materialsample. Section V below discloses methods for determining analyteconcentrations from sample spectra.

Section I—Fluid Handling System

FIG. 1 is a schematic of the fluid handling system 10 which includes thecontainer 15 supported by the stand 16 and having an interior that isfillable with the fluid 14, the catheter 11, and the sampling system100. Fluid handling system 10 includes one or more passageways 20 thatform conduits between the container, the sampling system, and thecatheter. Generally, sampling system 100 is adapted to accept a fluidsupply, such as fluid 14, and to be connected to a patient, including,but not limited to catheter 11 which is used to catheterize a patient P.Fluid 14 includes, but is not limited to, fluids for infusing a patientsuch as saline, lactated Ringer's solution, or water. Sampling system100, when so connected, is then capable of providing fluid to thepatient. In addition, sampling system 100 is also capable of drawingsamples, such as blood, from the patient through catheter 11 andpassageways 20, and analyzing at least a portion of the drawn sample.Sampling system 100 measures characteristics of the drawn sampleincluding, but not limited to, one or more of the blood plasma glucose,blood urea nitrogen (BUN), hematocrit, hemoglobin, or lactate levels.Optionally, sampling system 100 includes other devices or sensors tomeasure other patient or apparatus related information including, butnot limited to, patient blood pressure, pressure changes within thesampling system, or sample draw rate.

More specifically, FIG. 1 shows sampling system 100 as including thepatient connector 110, the fluid handling and analysis apparatus 140,and the connector 120. Sampling system 100 may include combinations ofpassageways, fluid control and measurement devices, and analysis devicesto direct, sample, and analyze fluid. Passageways 20 of sampling system100 include the fluid source passageway 111 from connector 120 to fluidhandling and analysis apparatus 140, the patient connection passageway112 from the fluid handling and analysis apparatus to patient connector110, and the sampling passageway 113 from the patient connector to thefluid handling and analysis apparatus. The reference of passageways 20as including one or more passageway, for example passageways 111, 112,and 113 are provided to facilitate discussion of the system. It isunderstood that passageways may include one or more separate componentsand may include other intervening components including, but not limitedto, pumps, valves, manifolds, and analytic equipment.

As used herein, the term “passageway” is a broad term and is used in itsordinary sense and includes, without limitation except as explicitlystated, as any opening through a material through which a fluid, such asa liquid or a gas, may pass so as to act as a conduit. Passagewaysinclude, but are not limited to, flexible, inflexible or partiallyflexible tubes, laminated structures having openings, bores throughmaterials, or any other structure that can act as a conduit and anycombination or connections thereof. The internal surfaces of passagewaysthat provide fluid to a patient or that are used to transport blood arepreferably biocompatible materials, including but not limited tosilicone, polyetheretherketone (PEEK), or polyethylene (PE). One type ofpreferred passageway is a flexible tube having a fluid contactingsurface formed from a biocompatible material. A passageway, as usedherein, also includes separable portions that, when connected, form apassageway.

The inner passageway surfaces may include coatings of various sorts toenhance certain properties of the conduit, such as coatings that affectthe ability of blood to clot or to reduce friction resulting from fluidflow. Coatings include, but are not limited to, molecular or ionictreatments.

As used herein, the term “connected” is a broad term and is used in itsordinary sense and includes, without limitation except as explicitlystated, with respect to two or more things (e.g., elements, devices,patients, etc.): a condition of physical contact or attachment, whetherdirect, indirect (via, e.g., intervening member(s)), continuous,selective, or intermittent; and/or a condition of being in fluid,electrical, or optical-signal communication, whether direct, indirect,continuous, selective (e.g., where there exist one or more interveningvalves, fluid handling components, switches, loads, or the like), orintermittent. A condition of fluid communication is considered to existwhether or not there exists a continuous or contiguous liquid or fluidcolumn extending between or among the two or more things in question.Various types of connectors can connect components of the fluid handlingsystem described herein. As used herein, the term “connector” is a broadterm and is used in its ordinary sense and includes, without limitationexcept as explicitly stated, as a device that connects passageways orelectrical wires to provide communication (whether direct, indirect,continuous, selective, or intermittent) on either side of the connector.Connectors contemplated herein include a device for connecting anyopening through which a fluid may pass. These connectors may haveintervening valves, switches, fluid handling devices, and the like foraffecting fluid flow. In some embodiments, a connector may also housedevices for the measurement, control, and preparation of fluid, asdescribed in several of the embodiments.

Fluid handling and analysis apparatus 140 may control the flow of fluidsthrough passageways 20 and the analysis of samples drawn from a patientP, as described subsequently. Fluid handling and analysis apparatus 140includes the display 141 and input devices, such as buttons 143. Display141 provides information on the operation or results of an analysisperformed by fluid handling and analysis apparatus 140. In oneembodiment, display 141 indicates the function of buttons 143, which areused to input information into fluid handling and analysis apparatus140. Information that may be input into or obtained by fluid handlingand analysis apparatus 140 includes, but is not limited to, a requiredinfusion or dosage rate, sampling rate, or patient specific informationwhich may include, but is not limited to, a patient identificationnumber or medical information. In an other alternative embodiment, fluidhandling and analysis apparatus 140 obtains information on patient Pover a communications network, for example an hospital communicationnetwork having patient specific information which may include, but isnot limited to, medical conditions, medications being administered,laboratory blood reports, gender, and weight. As one example of the useof fluid handling system 10, which is not meant to limit the scope ofthe present invention, FIG. 1 shows catheter 11 connected to patient P.

As discussed subsequently, fluid handling system 10 may catheterize apatient's vein or artery. Sampling system 100 is releasably connectableto container 15 and catheter 11. Thus, for example, FIG. 1 showscontainer 15 as including the tube 13 to provide for the passage offluid to, or from, the container, and catheter 11 as including the tube12 external to the patient. Connector 120 is adapted to join tube 13 andpassageway 111. Patient connector 110 is adapted to join tube 12 and toprovide for a connection between passageways 112 and 113.

Patient connector 110 may also include one or more devices that control,direct, process, or otherwise affect the flow through passageways 112and 113. In some embodiments, one or more lines 114 are provided toexchange signals between patient connector 110 and fluid handling andanalysis apparatus 140. The lines 114 can be electrical lines, opticalcommunicators, wireless communication channels, or other means forcommunication. As shown in FIG. 1, sampling system 100 may also includepassageways 112 and 113, and lines 114. The passageways and electricallines between apparatus 140 and patient connector 110 are referred to,with out limitation, as the bundle 130.

In various embodiments, fluid handling and analysis apparatus 140 and/orpatient connector 110, includes other elements (not shown in FIG. 1)that include, but are not limited to: fluid control elements, includingbut not limited to valves and pumps; fluid sensors, including but notlimited to pressure sensors, temperature sensors, hematocrit sensors,hemoglobin sensors, colorimetric sensors, and gas (or “bubble”) sensors;fluid conditioning elements, including but not limited to gas injectors,gas filters, and blood plasma separators; and wireless communicationdevices to permit the transfer of information within the sampling systemor between sampling system 100 and a wireless network.

In one embodiment, patient connector 110 includes devices to determinewhen blood has displaced fluid 14 at the connector end, and thusprovides an indication of when a sample is available for being drawnthrough passageway 113 for sampling. The presence of such a device atpatient connector 110 allows for the operation of fluid handling system10 for analyzing samples without regard to the actual length of tube 12.Accordingly, bundle 130 may include elements to provide fluids,including air, or information communication between patient connector110 and fluid handling and analysis apparatus 140 including, but notlimited to, one or more other passageways and/or wires.

In one embodiment of sampling system 100, the passageways and lines ofbundle 130 are sufficiently long to permit locating patient connector110 near patient P, for example with tube 12 having a length of lessthan 0.1 to 0.5 meters, or preferably approximately 0.15 meters and withfluid handling and analysis apparatus 140 located at a convenientdistance, for example on a nearby stand 16. Thus, for example, bundle130 is from 0.3 to 3 meters, or more preferably from 1.5 to 2.0 metersin length. It is preferred, though not required, that patient connector110 and connector 120 include removable connectors adapted for fittingto tubes 12 and 13, respectively. Thus, in one embodiment, container15/tube 13 and catheter 11/tube 12 are both standard medical components,and sampling system 100 allows for the easy connection and disconnectionof one or both of the container and catheter from fluid handling system10.

In another embodiment of sampling system 100, tubes 12 and 13 and asubstantial portion of passageways 111 and 112 have approximately thesame internal cross-sectional area. It is preferred, though notrequired, that the internal cross-sectional area of passageway 113 isless than that of passageways 111 and 112 (see FIG. 1B). As describedsubsequently, the difference in areas permits fluid handling system 10to transfer a small sample volume of blood from patient connector 110into fluid handling and analysis apparatus 140.

Thus, for example, in one embodiment passageways 111 and 112 are formedfrom a tube having an inner diameter from 0.3 millimeter to 1.50millimeter, or more preferably having a diameter from 0.60 millimeter to1.2 millimeter. Passageway 113 is formed from a tube having an innerdiameter from 0.3 millimeter to 1.5 millimeter, or more preferablyhaving an inner diameter of from 0.6 millimeter to 1.2 millimeter.

While FIG. 1 shows sampling system 100 connecting a patient to a fluidsource, the scope of the present disclosure is not meant to be limitedto this embodiment. Alternative embodiments include, but are not limitedto, a greater or fewer number of connectors or passageways, or theconnectors may be located at different locations within fluid handlingsystem 10, and alternate fluid paths. Thus, for example, passageways 111and 112 may be formed from one tube, or may be formed from two or morecoupled tubes including, for example, branches to other tubes withinsampling system 100, and/or there may be additional branches forinfusing or obtaining samples from a patient. In addition, patientconnector 110 and connector 120 and sampling system 100 alternativelyinclude additional pumps and/or valves to control the flow of fluid asdescribed below.

FIGS. 1A and 2 illustrate a sampling system 100 configured to analyzeblood from patient P which may be generally similar to the embodiment ofthe sampling system illustrated in FIG. 1, except as further detailedbelow. Where possible, similar elements are identified with identicalreference numerals in the depiction of the embodiments of FIGS. 1 to 2.FIGS. 1A and 2 show patient connector 110 as including a samplingassembly 220 and a connector 230, portions of passageways 111 and 113,and lines 114, and fluid handling and analysis apparatus 140 asincluding the pump 203, the sampling unit 200, and a controller 210. Thepump 203, sampling unit 200, and controller 210 are contained within ahousing 209 of the fluid handling and analysis apparatus 140. Thepassageway 111 extends from the connector 120 through the housing 209 tothe pump 203. The bundle 130 extends from the pump 203, sampling unit200, and controller 210 to the patient connector 110.

In FIGS. 1A and 2, the passageway 111 provides fluid communicationbetween connector 120 and pump 203 and passageway 113 provides fluidcommunication between pump 203 and connector 110. Controller 210 is incommunication with pump 203, sampling unit 200, and sampling assembly220 through lines 114. Controller 210 has access to memory 212, andoptionally has access to a media reader 214, including but not limitedto a DVD or CD-ROM reader, and communications link 216, which cancomprise a wired or wireless communications network, including but notlimited to a dedicated line, an intranet, or an Internet connection.

As described subsequently in several embodiments, sampling unit 200 mayinclude one or more passageways, pumps and/or valves, and samplingassembly 220 may include passageways, sensors, valves, and/or sampledetection devices. Controller 210 collects information from sensors anddevices within sampling assembly 220, from sensors and analyticalequipment within sampling unit 200, and provides coordinated signals tocontrol pump 203 and pumps and valves, if present, in sampling assembly220.

Fluid handling and analysis apparatus 140 includes the ability to pumpin a forward direction (towards the patient) and in a reverse direction(away from the patient). Thus, for example, pump 203 may direct fluid 14into patient P or draw a sample, such as a blood sample from patient P,from catheter 11 to sampling assembly 220, where it is further directedthrough passageway 113 to sampling unit 200 for analysis. Preferably,pump 203 provides a forward flow rate at least sufficient to keep thepatient vascular line open. In one embodiment, the forward flow rate isfrom 1 to 5 ml/hr. In some embodiments, the flow rate of fluid is about0.05 ml/hr, 0.1 ml/hr, 0.2 ml/hr, 0.4 ml/hr, 0.6 ml/hr, 0.8 ml/hr, 1.0ml/hr, and ranges encompassing such flow rates. In some embodiments, forexample, the flow rate of fluid is less than about 1.0 ml/hr. In certainembodiments, the flow rate of fluid may be about 0.1 ml/hr or less. Whenoperated in a reverse direction, fluid handling and analysis apparatus140 includes the ability to draw a sample from the patient to samplingassembly 220 and through passageway 113. In one embodiment, pump 203provides a reverse flow to draw blood to sampling assembly 220,preferably by a sufficient distance past the sampling assembly to ensurethat the sampling assembly contains an undiluted blood sample. In oneembodiment, passageway 113 has an inside diameter of from 25 to 200microns, or more preferably from 50 to 100 microns. Sampling unit 200extracts a small sample, for example from 10 to 100 microliters ofblood, or more preferably approximately 40 microliters volume of blood,from sampling assembly 220.

In one embodiment, pump 203 is a directionally controllable pump thatacts on a flexible portion of passageway 111. Examples of a single,directionally controllable pump include, but are not limited to areversible peristaltic pump or two unidirectional pumps that work inconcert with valves to provide flow in two directions. In an alternativeembodiment, pump 203 includes a combination of pumps, including but notlimited to displacement pumps, such as a syringe, and/or valve toprovide bi-directional flow control through passageway 111.

Controller 210 includes one or more processors for controlling theoperation of fluid handling system 10 and for analyzing samplemeasurements from fluid handling and analysis apparatus 140. Controller210 also accepts input from buttons 143 and provides information ondisplay 141. Optionally, controller 210 is in bi-directionalcommunication with a wired or wireless communication system, for examplea hospital network for patient information. The one or more processorscomprising controller 210 may include one or more processors that arelocated either within fluid handling and analysis apparatus 140 or thatare networked to the unit.

The control of fluid handling system 10 by controller 210 may include,but is not limited to, controlling fluid flow to infuse a patient and tosample, prepare, and analyze samples. The analysis of measurementsobtained by fluid handling and analysis apparatus 140 of may include,but is not limited to, analyzing samples based on inputted patientspecific information, from information obtained from a databaseregarding patient specific information, or from information providedover a network to controller 210 used in the analysis of measurements byapparatus 140.

Fluid handling system 10 provides for the infusion and sampling of apatient blood as follows. With fluid handling system 10 connected to bag15 having fluid 14 and to a patient P, controller 210 infuses a patientby operating pump 203 to direct the fluid into the patient. Thus, forexample, in one embodiment, the controller directs that samples beobtained from a patient by operating pump 203 to draw a sample. In oneembodiment, pump 203 draws a predetermined sample volume, sufficient toprovide a sample to sampling assembly 220. In another embodiment, pump203 draws a sample until a device within sampling assembly 220 indicatesthat the sample has reached the patient connector 110. As an examplewhich is not meant to limit the scope of the present invention, one suchindication is provided by a sensor that detects changes in the color ofthe sample. Another example is the use of a device that indicateschanges in the material within passageway 111 including, but not limitedto, a decrease in the amount of fluid 14, a change with time in theamount of fluid, a measure of the amount of hemoglobin, or an indicationof a change from fluid to blood in the passageway.

When the sample reaches sampling assembly 220, controller 210 providesan operating signal to valves and/or pumps in sampling system 100 (notshown) to draw the sample from sampling assembly 220 into sampling unit200. After a sample is drawn towards sampling unit 200, controller 210then provides signals to pump 203 to resume infusing the patient. In oneembodiment, controller 210 provides signals to pump 203 to resumeinfusing the patient while the sample is being drawn from samplingassembly 220. In an alternative embodiment, controller 210 providessignals to pump 203 to stop infusing the patient while the sample isbeing drawn from sampling assembly 220. In another alternativeembodiment, controller 210 provides signals to pump 203 to slow thedrawing of blood from the patient while the sample is being drawn fromsampling assembly 220.

In another alternative embodiment, controller 210 monitors indicationsof obstructions in passageways or catheterized blood vessels duringreverse pumping and moderates the pumping rate and/or direction of pump203 accordingly. Thus, for example, obstructed flow from an obstructedor kinked passageway or of a collapsing or collapsed catheterized bloodvessel that is being pumped will result in a lower pressure than anunobstructed flow. In one embodiment, obstructions are monitored using apressure sensor in sampling assembly 220 or along passageways 20. If thepressure begins to decrease during pumping, or reaches a value that islower than a predetermined value then controller 210 directs pump 203 todecrease the reverse pumping rate, stop pumping, or pump in the forwarddirection in an effort to reestablish unobstructed pumping.

FIG. 3 is a schematic showing details of a sampling system 300 which maybe generally similar to the embodiments of sampling system 100 asillustrated in FIGS. 1 and 2, except as further detailed below. Samplingsystem 300 includes sampling assembly 220 having, along passageway 112:connector 230 for connecting to tube 12, a pressure sensor 317, acolorimetric sensor 311, a first bubble sensor 314 a, a first valve 312,a second valve 313, and a second bubble sensor 314 b. Passageway 113forms a “T” with passageway 111 at a junction 318 that is positionedbetween the first valve 312 and second valve 313, and includes a gasinjector manifold 315 and a third valve 316. The lines 114 comprisecontrol and/or signal lines extending from calorimetric sensor 311,first, second, and third valves (312, 313, 316), first and second bubblesensors (314 a, 314 b), gas injector manifold 315, and pressure sensor317. Sampling system 300 also includes sampling unit 200 which has abubble sensor 321, a sample analysis device 330, a first valve 323 a, awaste receptacle 325, a second valve 323 b, and a pump 328. Passageway113 forms a “T” to form a waste line 324 and a pump line 327.

It is preferred, though not necessary, that the sensors of samplingsystem 100 are adapted to accept a passageway through which a sample mayflow and that sense through the walls of the passageway. As describedsubsequently, this arrangement allows for the sensors to be reusable andfor the passageways to be disposable. It is also preferred, though notnecessary, that the passageway is smooth and without abrupt dimensionalchanges which may damage blood or prevent smooth flow of blood. Inaddition, is also preferred that the passageways that deliver blood fromthe patient to the analyzer not contain gaps or size changes that permitfluid to stagnate and not be transported through the passageway.

In one embodiment, the respective passageways on which valves 312, 313,316, and 323 are situated along passageways that are flexible tubes, andvalves 312, 313, 316, and 323 are “pinch valves,” in which one or moremovable surfaces compress the tube to restrict or stop flowtherethrough. In one embodiment, the pinch valves include one or moremoving surfaces that are actuated to move together and “pinch” aflexible passageway to stop flow therethrough. Examples of a pinch valveinclude, for example, Model PV256 Low Power Pinch Valve (InstechLaboratories, Inc., Plymouth Meeting, Pa.). Alternatively, one or moreof valves 312, 313, 316, and 323 may be other valves for controlling theflow through their respective passageways.

Colorimetric sensor 311 accepts or forms a portion of passageway 111 andprovides an indication of the presence or absence of blood within thepassageway. In one embodiment, calorimetric sensor 311 permitscontroller 210 to differentiate between fluid 14 and blood. Preferably,colorimetric sensor 311 is adapted to receive a tube or other passagewayfor detecting blood. This permits, for example, a disposable tube to beplaced into or through a reusable colorimetric sensor. In an alternativeembodiment, colorimetric sensor 311 is located adjacent to bubble sensor314 b. Examples of a colorimetric sensor include, for example, anOptical Blood Leak/Blood vs. Saline Detector available from IntrotekInternational (Edgewood, N.J.).

As described subsequently, sampling system 300 injects a gas—referred toherein and without limitation as a “bubble”—into passageway 113.Sampling system 300 includes gas injector manifold 315 at or nearjunction 318 to inject one or more bubbles, each separated by liquid,into passageway 113. The use of bubbles is useful in preventinglongitudinal mixing of liquids as they flow through passageways both inthe delivery of a sample for analysis with dilution and for cleaningpassageways between samples. Thus, for example the fluid in passageway113 includes, in one embodiment of the invention, two volumes ofliquids, such as sample S or fluid 14 separated by a bubble, or multiplevolumes of liquid each separated by a bubble therebetween.

Bubble sensors 314 a, 314 b and 321 each accept or form a portion ofpassageway 112 or 113 and provide an indication of the presence of air,or the change between the flow of a fluid and the flow of air, throughthe passageway. Examples of bubble sensors include, but are not limitedto ultrasonic or optical sensors, that can detect the difference betweensmall bubbles or foam from liquid in the passageway. Once such bubbledetector is an MEC Series Air Bubble/Liquid Detection Sensor (IntrotekInternational, Edgewood, N.Y.). Preferably, bubble sensor 314 a, 314 b,and 321 are each adapted to receive a tube or other passageway fordetecting bubbles. This permits, for example, a disposable tube to beplaced through a reusable bubble sensor.

Pressure sensor 317 accepts or forms a portion of passageway 111 andprovides an indication or measurement of a fluid within the passageway.When all valves between pressure sensor 317 and catheter 11 are open,pressure sensor 317 provides an indication or measurement of thepressure within the patient's catheterized blood vessel. In oneembodiment, the output of pressure sensor 317 is provided to controller210 to regulate the operation of pump 203. Thus, for example, a pressuremeasured by pressure sensor 317 above a predetermined value is taken asindicative of a properly working system, and a pressure below thepredetermined value is taken as indicative of excessive pumping due to,for example, a blocked passageway or blood vessel. Thus, for example,with pump 203 operating to draw blood from patient P, if the pressure asmeasured by pressure sensor 317 is within a range of normal bloodpressures, it may be assumed that blood is being drawn from the patientand pumping continues. However, if the pressure as measured by pressuresensor 317 falls below some level, then controller 210 instructs pump203 to slow or to be operated in a forward direction to reopen the bloodvessel. One such pressure sensor is a Deltran IV part number DPT-412(Utah Medical Products, Midvale, Utah).

Sample analysis device 330 receives a sample and performs an analysis.In several embodiments, device 330 is configured to prepare of thesample for analysis. Thus, for example, device 330 may include a samplepreparation unit 332 and an analyte detection system 334, where thesample preparation unit is located between the patient and the analytedetection system. In general, sample preparation occurs between samplingand analysis. Thus, for example, sample preparation unit 332 may takeplace removed from analyte detection, for example within samplingassembly 220, or may take place adjacent or within analyte detectionsystem 334.

As used herein, the term “analyte” is a broad term and is used in itsordinary sense and includes, without limitation, any chemical speciesthe presence or concentration of which is sought in the material sampleby an analyte detection system. For example, the analyte(s) include, butnot are limited to, glucose, ethanol, insulin, water, carbon dioxide,blood oxygen, cholesterol, bilirubin, ketones, fatty acids,lipoproteins, albumin, urea, creatinine, white blood cells, red bloodcells, hemoglobin, oxygenated hemoglobin, carboxyhemoglobin, organicmolecules, inorganic molecules, pharmaceuticals, cytochrome, variousproteins and chromophores, microcalcifications, electrolytes, sodium,potassium, chloride, bicarbonate, and hormones. As used herein, the term“material sample” (or, alternatively, “sample”) is a broad term and isused in its ordinary sense and includes, without limitation, anycollection of material which is suitable for analysis. For example, amaterial sample may comprise whole blood, blood components (e.g., plasmaor serum), interstitial fluid, intercellular fluid, saliva, urine, sweatand/or other organic or inorganic materials, or derivatives of any ofthese materials. In one embodiment, whole blood or blood components maybe drawn from a patient's capillaries.

In one embodiment, sample preparation unit 332 separates blood plasmafrom a whole blood sample or removes contaminants from a blood sampleand thus comprises one or more devices including, but not limited to, afilter, membrane, centrifuge, or some combination thereof. Inalternative embodiments, analyte detection system 334 is adapted toanalyze the sample directly and sample preparation unit 332 is notrequired.

Generally, sampling assembly 220 and sampling unit 200 direct the fluiddrawn from sampling assembly 220 into passageway 113 into sampleanalysis device 330. FIG. 4 is a schematic of an embodiment of asampling unit 400 that permits some of the sample to bypass sampleanalysis device 330. Sampling unit 400 may be generally similar tosampling unit 200, except as further detailed below. Sampling unit 400includes bubble sensor 321, valve 323, sample analysis device 330, wasteline 324, waste receptacle 325, valve 326, pump line 327, pump 328, avalve 322, and a waste line 329. Waste line 329 includes valve 322 andforms a “T” at pump line 337 and waste line 329. Valves 316, 322, 323,and 326 permit a flow through passageway 113 to be routed through sampleanalysis device 330, to be routed to waste receptacle 325, or to berouted through waste line 324 to waste receptacle 325.

FIG. 5 is a schematic of one embodiment of a sampling system 500 whichmay be generally similar to the embodiments of sampling system 100 or300 as illustrated in FIGS. 1 through 4, except as further detailedbelow. Sampling system 500 includes an embodiment of a sampling unit 510and differs from sampling system 300 in part, in that liquid drawn frompassageway 111 may be returned to passageway 111 at a junction 502between pump 203 and connector 120.

With reference to FIG. 5, sampling unit 510 includes a return line 503that intersects passageway 111 on the opposite side of pump 203 frompassageway 113, a bubble sensor 505 and a pressure sensor 507, both ofwhich are controlled by controller 210. Bubble sensor 505 is generallysimilar to bubble sensors 314 a, 314 b and 321 and pressure sensor 507is generally similar to pressure sensor 317. Pressure sensor 507 isuseful in determining the correct operation of sampling system 500 bymonitoring pressure in passageway 111. Thus, for example, the pressurein passageway 111 is related to the pressure at catheter 11 whenpressure sensor 507 is in fluid communication with catheter 11 (that is,when any intervening valve(s) are open). The output of pressure sensor507 is used in a manner similar to that of pressure sensor 317 describedpreviously in controlling pumps of sampling system 500.

Sampling unit 510 includes valves 501, 326 a, and 326 b under thecontrol of controller 210. Valve 501 provides additional liquid flowcontrol between sampling unit 200 and sampling unit 510. Pump 328 ispreferably a bi-directional pump that can draw fluid from and intopassageway 113. Fluid may either be drawn from and returned topassageway 501, or may be routed to waste receptacle 325. Valves 326 aand 326 b are situated on either side of pump 328. Fluid can be drawnthrough passageway 113 and into return line 503 by the coordinatedcontrol of pump 328 and valves 326 a and 326 b. Directing flow fromreturn line 503 can be used to prime sampling system 500 with fluid.Thus, for example, liquid may be pulled into sampling unit 510 byoperating pump 328 to pull liquid from passageway 113 while valve 326 ais open and valve 326 b is closed. Liquid may then be pumped back intopassageway 113 by operating pump 328 to push liquid into passageway 113while valve 326 a is closed and valve 326 b is open.

FIG. 6A is a schematic of an embodiment of gas injector manifold 315which may be generally similar or included within the embodimentsillustrated in FIGS. 1 through 5, except as further detailed below. Gasinjector manifold 315 is a device that injects one or more bubbles in aliquid within passageway 113 by opening valves to the atmosphere andlowering the liquid pressure within the manifold to draw in air. Asdescribed subsequently, gas injector manifold 315 facilitates theinjection of air or other gas bubbles into a liquid within passageway113. Gas injector manifold 315 has three gas injectors 610 including afirst injector 610 a, a second injector 610 b, and a third injector 610c. Each injector 610 includes a corresponding passageway 611 that beginsat one of several laterally spaced locations along passageway 113 andextends through a corresponding valve 613 and terminates at acorresponding end 615 that is open to the atmosphere. In an alternativeembodiment, a filter is placed in end 615 to filter out dust orparticles in the atmosphere. As described subsequently, each injector610 is capable of injecting a bubble into a liquid within passageway 113by opening the corresponding valve 613, closing a valve on one end ofpassageway 113 and operating a pump on the opposite side of thepassageway to lower the pressure and pull atmospheric air into thefluid. In one embodiment of gas injector manifold 315, passageways 113and 611 are formed within a single piece of material (e.g., as boresformed in or through a plastic or metal housing (not shown)). In analternative embodiment, gas injector manifold 315 includes fewer thanthree injectors, for example one or two injectors, or includes more thanthree injectors. In another alternative embodiment, gas injectormanifold 315 includes a controllable high pressure source of gas forinjection into a liquid in passageway 113. It is preferred that valves613 are located close to passageway 113 to minimize trapping of fluid inpassageways 611.

Importantly, gas injected into passageways 20 should be prevented fromreaching catheter 11. As a safety precaution, one embodiment preventsgas from flowing towards catheter 11 by the use of bubble sensor 314 aas shown, for example, in FIG. 3. If bubble sensor 314 a detects gaswithin passageway 111, then one of several alternative embodimentsprevents unwanted gas flow. In one embodiment, flow in the vicinity ofsampling assembly 220 is directed into line 113 or through line 113 intowaste receptacle 325. With further reference to FIG. 3, upon thedetection of gas by bubble sensor 314 a, valves 316 and 323 a areopened, valve 313 and the valves 613 a, 613 b and 613 c of gas injectormanifold 315 are closed, and pump 328 is turned on to direct flow awayfrom the portion of passageway 111 between sampling assembly 220 andpatient P into passageway 113. Bubble sensor 321 is monitored to providean indication of when passageway 113 clears out. Valve 313 is thenopened, valve 312 is closed, and the remaining portion of passageway 111is then cleared. Alternatively, all flow is immediately halted in thedirection of catheter 11, for example by closing all valves and stoppingall pumps. In an alternative embodiment of sampling assembly 220, agas-permeable membrane is located within passageway 113 or within gasinjector manifold 315 to remove unwanted gas from fluid handling system10, e.g., by venting such gas through the membrane to the atmosphere ora waste receptacle.

FIG. 6B is a schematic of an embodiment of gas injector manifold 315′which may be generally similar to, or included within, the embodimentsillustrated in FIGS. 1 through 6A, except as further detailed below. Ingas injector manifold 315′, air line 615 and passageway 113 intersect atjunction 318. Bubbles are injected by opening valve 316 and 613 whiledrawing fluid into passageway 113. Gas injector manifold 315′ is thusmore compact that gas injector manifold 315, resulting in a morecontrollable and reliable gas generator.

Section II—Fluid Handling Methods

One embodiment of a method of using fluid handling system 10, includingsampling assembly 220 and sampling unit 200 of FIGS. 2, 3 and 6A, isillustrated in Table 1 and in the schematic fluidic diagrams of FIGS.7A-7J. In general, the pumps and valves are controlled to infuse apatient, to extract a sample from the patient up passageway 111 topassageway 113, and to direct the sample along passageway 113 to device330. In addition, the pumps and valves are controlled to inject bubblesinto the fluid to isolate the fluid from the diluting effect of previousfluid and to clean the lines between sampling. The valves in FIGS. 7A-7Jare labeled with suffices to indicate whether the valve is open orclosed. Thus a valve “x,” for example, is shown as valve “x-o” if thevalve is open and “x-c” if the valve is closed.

TABLE 1 Methods of operating system 10 as illustrated in FIGS. 7A-7JPump Pump Valve Valve Valve Valve Valve Valve Valve Valve Mode Step 203328 312 313 613a 613b 613c 316 323a 323b Infuse (FIG. 7A) F Off O O C CC C C C patient Infuse patient Sample (FIG. 7B) R Off C O one or more CC C patient Clear fluid from are open passageways O O O (FIG. 7C) R OffO O C C C C C C Draw sample until after colorimetric sensor 311 sensesblood (FIG. 7D) Off On O C C C C O C O Inject sample into bubblemanifold Alternative to R On O O C C C O C O FIG. 7D (FIG. 7E) Off On CC sequentially O C O Inject bubbles O O O (FIG. 7F) F Off C O C C C O OC Clear bubbles from patient line (FIG. 7G) F Off O O C C C C C C Clearblood from patient line (FIG. 7H) F Off C O C C C O O C Move bubbles outof bubbler (FIG. 7I) Add Off On C C sequentially O C O cleaning bubblesO O O (FIG. 7J) Push F Off C O C C C O O C sample to analyzer untilbubble sensor 321 detects bubble F = Forward (fluid into patient), R =Reverse (fluid from patient), O = Open, C = Closed

FIG. 7A illustrates one embodiment of a method of infusing a patient. Inthe step of FIG. 7A, pump 203 is operated forward (pumping towards thepatient) pump 328 is off, or stopped, valves 313 and 312 are open, andvalves 613 a, 613 b, 613 c, 316, 323 a, and 323 b are closed. With theseoperating conditions, fluid 14 is provided to patient P. In a preferredembodiment, all of the other passageways at the time of the step of FIG.7A substantially contain fluid 14.

The next nine figures (FIGS. 7B-7J) illustrate steps in a method ofsampling from a patient. The following steps are not meant to beinclusive of all of the steps of sampling from a patient, and it isunderstood that alternative embodiments may include more steps, fewersteps, or a different ordering of steps. FIG. 7B illustrates a firstsampling step, where liquid is cleared from a portion of patientconnection passageway and sampling passageways 112 and 113. In the stepof FIG. 7B, pump 203 is operated in reverse (pumping away from thepatient), pump 328 is off, valve 313 is open, one or more of valves 613a, 613 b, and 613 c are open, and valves 312, 316, 323 a, and 326 b areclosed. With these operating conditions, air 701 is drawn into samplingpassageway 113 and back into patient connection passageway 112 untilbubble sensor 314 b detects the presence of the air.

FIG. 7C illustrates a second sampling step, where a sample is drawn frompatient P into patient connection passageway 112. In the step of FIG.7C, pump 203 is operated in reverse, pump 328 is off, valves 312 and 313are open, and valves 316, 613 a, 613 b, 613 c, 323 a, and 323 b areclosed. Under these operating conditions, a sample S is drawn intopassageway 112, dividing air 701 into air 701 a within samplingpassageway 113 and air 701 b within the patient connection passageway112. Preferably this step proceeds until sample S extends just past thejunction of passageways 112 and 113. In one embodiment, the step of FIG.7C proceeds until variations in the output of colorimetric sensor 311indicate the presence of a blood (for example by leveling off to aconstant value), and then proceeds for an additional set amount of timeto ensure the presence of a sufficient volume of sample S.

FIG. 7D illustrates a third sampling step, where a sample is drawn intosampling passageway 113. In the step of FIG. 7D, pump 203 is off, orstopped, pump 328 is on, valves 312, 316, and 326 b are open, and valves313, 613 a, 613 b, 613 c and 323 a are closed. Under these operatingconditions, blood is drawn into passageway 113. Preferably, pump 328 isoperated to pull a sufficient amount of sample S into passageway 113. Inone embodiment, pump 328 draws a sample S having a volume from 30 to 50microliters. In an alternative embodiment, the sample is drawn into bothpassageways 112 and 113. Pump 203 is operated in reverse, pump 328 ison, valves 312, 313, 316, and 323 b are open, and valves 613 a, 613 b,613 c and 323 a are closed to ensure fresh blood in sample S.

FIG. 7E illustrates a fourth sampling step, where air is injected intothe sample. Bubbles which span the cross-sectional area of samplingpassageway 113 are useful in preventing contamination of the sample asit is pumped along passageway 113. In the step of FIG. 7E, pump 203 isoff, or stopped, pump 328 is on, valves 316, and 323 b are open, valves312, 313 and 323 a are closed, and valves 613 a, 613 b, 613 c are eachopened and closed sequentially to draw in three separated bubbles. Withthese operating conditions, the pressure in passageway 113 falls belowatmospheric pressure and air is drawn into passageway 113.Alternatively, valves 613 a, 613 b, 613 c may be opened simultaneouslyfor a short period of time, generating three spaced bubbles. As shown inFIG. 7E, injectors 610 a, 610 b, and 610 c inject bubbles 704, 703, and702, respectively, dividing sample S into a forward sample S1, a middlesample S2, and a rear sample S3.

FIG. 7F illustrates a fifth sampling step, where bubbles are clearedfrom patient connection passageway 112. In the step of FIG. 7F, pump 203is operated in a forward direction, pump 328 is off, valves 313, 316,and 323 a are open, and valves 312, 613 a, 613 b, 613 c, and 323 b areclosed. With these operating conditions, the previously injected air 701b is drawn out of first passageway 111 and into second passageway 113.This step proceeds until air 701 b is in passageway 113.

FIG. 7G illustrates a sixth sampling step, where blood in passageway 112is returned to the patient. In the step of FIG. 7G, pump 203 is operatedin a forward direction, pump 328 is off, valves 312 and 313 are open,and valves 316, 323 a, 613 a, 613 b, 613 c and 323 b are closed. Withthese operating conditions, the previously injected air remains inpassageway 113 and passageway 111 is filled with fluid 14.

FIGS. 7H and 7I illustrates a seventh and eighth sampling steps, wherethe sample is pushed part way into passageway 113 followed by fluid 14and more bubbles. In the step of FIG. 7H, pump 203 is operated in aforward direction, pump 328 is off, valves 313, 316, and 323 a are open,and valves 312, 613 a, 613 b, 613 c, and 323 b are closed. With theseoperating conditions, sample S is moved partway into passageway 113 withbubbles injected, either sequentially or simultaneously, into fluid 14from injectors 610 a, 610 b, and 610 c. In the step of FIG. 7I, thepumps and valves are operated as in the step of FIG. 7E, and fluid 14 isdivided into a forward solution C1, a middle solution C2, and a rearsolution C3 separated by bubbles 705, 706, and 707.

The last step shown in FIG. 7 is FIG. 7J, where middle sample S2 ispushed to sample analysis device 330. In the step of FIG. 7J, pump 203is operated in a forward direction, pump 328 is off, valves 313, 316,and 323 a are open, and valves 312, 613 a, 613 b, 613 c, and 323 b areclosed. In this configuration, the sample is pushed into passageway 113.When bubble sensor 321 detects bubble 702, pump 203 continues pumpinguntil sample S 2 is taken into device sample analysis 330. Additionalpumping using the settings of the step of FIG. 7J permits the sample S2to be analyzed and for additional bubbles and solutions to be pushedinto waste receptacle 325, cleansing passageway 113 prior to accepting anext sample.

Section III—Sampling System

FIG. 8 is a perspective front view of a third embodiment of a samplingsystem 800 of the present invention which may be generally similar tosampling system 100, 300 or 500 and the embodiments illustrated in FIGS.1 through 7, except as further detailed below. The fluid handling andanalysis apparatus 140 of sampling system 800 includes the combinationof an instrument 810 and a sampling system cassette 820. FIG. 8illustrates instrument 810 and cassette 820 partially removed from eachother. Instrument 810 includes controller 210 (not shown), display 141and input devices 143, a cassette interface 811, and lines 114. Cassette820 includes passageway 111 which extends from connector 120 toconnector 230, and further includes passageway 113, a junction 829 ofpassageways 111 and 113, an instrument interface 821, a front surface823, an inlet 825 for passageway 111, and an inlet 827 for passageways111 and 113. In addition, sampling assembly 220 is formed from asampling assembly instrument portion 813 having an opening 815 foraccepting junction 829. The interfaces 811 and 821 engage the componentsof instrument 810 and cassette 820 to facilitate pumping fluid andanalyzing samples from a patient, and sampling assembly instrumentportion 813 accepts junction 829 in opening 815 to provide for samplingfrom passageway 111.

FIGS. 9 and 10 are front views of a sampling system cassette 820 andinstrument 810, respectively, of a sampling system 800. Cassette 820 andinstrument 810, when assembled, form various components of FIGS. 9 and10 that cooperate to form an apparatus consisting of sampling unit 510of FIG. 5, sampling assembly 220 of FIG. 3, and gas injection manifold315′ of FIG. 6B.

More specifically, as shown in FIG. 9, cassette 820 includes passageways20 including: passageway 111 having portions 111 a, 112 a, 112 b, 112 c,112 d, 112 e, and 112 f; passageway 113 having portions 113 a, 113 b,113 c, 113 d, 113 e, and 113 f; passageway 615; waste receptacle 325;disposable components of sample analysis device 330 including, forexample, a sample preparation unit 332 adapted to allow only bloodplasma to pass therethrough and a sample chamber 903 for placementwithin analyte detection system 334 for measuring properties of theblood plasma; and a displacement pump 905 having a piston control 907.

As shown in FIG. 10, instrument 810 includes bubble sensor units 1001 a,1001 b, and 1001 c, colorimetric sensor, which is a hemoglobin sensorunit 1003, a peristaltic pump roller 1005 a and a roller support 1005 b,pincher pairs 1007 a, 1007 b, 1007 c, 1007 d, 1007 e, 1007 f, 1007 g,and 1007 h, an actuator 1009, and a pressure sensor unit 1011. Inaddition, instrument 810 includes portions of sample analysis device 330which are adapted to measure a sample contained within sample chamber903 when located near or within a probe region 1002 of an opticalanalyte detection system 334.

Passageway portions of cassette 820 contact various components ofinstrument 810 to form sampling system 800. With reference to FIG. 5 forexample, pump 203 is formed from portion 111 a placed betweenperistaltic pump roller 1005 a and roller support 1005 b to move fluidthrough passageway 111 when the roller is actuated; valves 501, 323, 326a, and 326 b are formed with pincher pairs 1007 a, 1007 b, 1007 c, and1007 d surrounding portions 113 a, 113 c, 113 d, and 113 e,respectively, to permit or block fluid flow therethrough. Pump 328 isformed from actuator 1009 positioned to move piston control 907. It ispreferred that the interconnections between the components of cassette820 and instrument 810 described in this paragraph are made with onemotion. Thus for example the placement of interfaces 811 and 821 placesthe passageways against and/or between the sensors, actuators, and othercomponents.

In addition to placement of interface 811 against interface 821, theassembly of apparatus 800 includes assembling sampling assembly 220.More specifically, an opening 815 a and 815 b are adapted to receivepassageways 111 and 113, respectively, with junction 829 within samplingassembly instrument portion 813. Thus, for example, with reference toFIG. 3, valves 313 and 312 are formed when portions 112 b and 112 c areplaced within pinchers of pinch valves 1007 e and 1007 f, respectively,bubble sensors 314 b and 314 a are formed when bubble sensor units 1001b, and 1001 c are in sufficient contact with portions 112 a and 112 d,respectively, to determine the presence of bubbles therein; hemoglobindetector is formed when hemoglobin sensor 1003 is in sufficient contactwith portion 112 e, and pressure sensor 317 is formed when portion 112 fis in sufficient contact with pressure sensor unit 1011 to measure thepressure of a fluid therein. With reference to FIG. 6B, valves 316 and613 are formed when portions 113 f and 615 are placed within pinchers ofpinch valves 1007 h and 1007 g, respectively.

In operation, the assembled main instrument 810 and cassette 820 ofFIGS. 9-10 can function as follows. The system can be considered tobegin in an idle state or infusion mode in which the roller pump 1005operates in a forward direction (with the impeller 1005 a turningcounterclockwise as shown in FIG. 10) to pump infusion fluid from thecontainer 15 through the passageway 111 and the passageway 112, towardand into the patient P. In this infusion mode the pump 1005 deliversinfusion fluid to the patient at a suitable infusion rate as discussedelsewhere herein.

When it is time to conduct a measurement, air is first drawn into thesystem to clear liquid from a portion of the passageways 112, 113, in amanner similar to that shown in FIG. 7B. Here, the single air injectorof FIG. 9 (extending from the junction 829 to end 615, opposite thepassageway 813 ) functions in place of the manifold shown in FIGS.7A-7J. Next, to draw a sample, the pump 1005 operates in a sample drawmode, by operating in a reverse direction and pulling a sample of bodilyfluid (e.g. blood) from the patient into the passageway 112 through theconnector 230. The sample is drawn up to the hemoglobin sensor 1003, andis preferably drawn until the output of the sensor 1003 reaches adesired plateau level indicating the presence of an undiluted bloodsample in the passageway 112 adjacent the sensor 1003.

From this point the pumps 905, 1005, valves 1007 e, 1007 f, 1007 g, 1007h, bubble sensors 1001 b, 1001 c and/or hemoglobin sensor 1003 can beoperated to move a series of air bubbles and sample-fluid columns intothe passageway 113, in a manner similar to that shown in FIGS. 7D-7F.The pump 905, in place of the pump 328, is operable by moving the pistoncontrol 907 of the pump 905 in the appropriate direction (to the left orright as shown in FIGS. 9-10) with the actuator 1009.

Once a portion of the bodily fluid sample and any desired bubbles havemoved into the passageway 113, the valve 1007 h can be closed, and theremainder of the initial drawn sample or volume of bodily fluid in thepassageway 112 can be returned to the patient, by operating the pump1005 in the forward or infusion direction until the passageway 112 isagain filled with infusion fluid.

With appropriate operation of the valves 1007 a-1007 h, and the pump(s)905 and/or 1005, at least a portion of the bodily fluid sample in thepassageway 113 (which is 10-100 microliters in volume, or 20, 30, 40, 50or 60 microliters, in various embodiments) is moved through the samplepreparation unit 332 (in the depicted embodiment a filter or membrane;alternatively a centrifuge as discussed in greater detail below). Thus,only one or more components of the bodily fluid (e.g., only the plasmaof a blood sample) passes through the unit 332 or filter/membrane andenters the sample chamber or cell 903. Alternatively, where the unit 332is omitted, the “whole” fluid moves into the sample chamber 903 foranalysis.

Once the component(s) or whole fluid is in the sample chamber 903, theanalysis is conducted to determine a level or concentration of one ormore analytes, such as glucose, lactate, carbon dioxide, blood ureanitrogen, hemoglobin, and/or any other suitable analytes as discussedelsewhere herein. Where the analyte detection system 1700 isspectroscopic (e.g. the system 1700 of FIGS. 17 or 44-46), aspectroscopic analysis of the component(s) or whole fluid is conducted.

After the analysis, the body fluid sample within the passageway 113 ismoved into the waste receptacle 325. Preferably, the pump 905 isoperated via the actuator 1009 to push the body fluid, behind a columnof saline or infusion fluid obtained via the passageway 909, backthrough the sample chamber 903 and sample preparation unit 332, and intothe receptacle 325. Thus, the chamber 903 and unit 332 are back-flushedand filled with saline or infusion fluid while the bodily fluid isdelivered to the waste receptacle. Following this flush a secondanalysis can be made on the saline or infusion fluid now in the chamber903, to provide a “zero” or background reading. At this point, the fluidhandling network of FIG. 9, other than the waste receptacle 325, isempty of bodily fluid, and the system is ready to draw another bodilyfluid sample for analysis.

In some embodiments of the apparatus 140, a pair of pinch valve pinchersacts to switch flow between one of two branches of a passageway. FIGS.13A and 13B are front view and sectional view, respectively, of a firstembodiment pinch valve 1300 in an open configuration that can directflow either one or both of two branches, or legs, of a passageway. Pinchvalve 1300 includes two separately controllable pinch valves acting on a“Y” shaped passageway 1310 to allow switch of fluid between variouslegs. In particular, the internal surface of passageway 1310 forms afirst leg 1311 having a flexible pinch region 1312, a second leg 1313having a flexible pinch region 1314, and a third leg 1315 that joins thefirst and second legs at an intersection 1317. A first pair of pinchvalve pinchers 1320 is positioned about pinch region 1312 and a secondpair of pinch valve pinchers 1330 is positioned about pinch region 1314.Each pair of pinch valve pinchers 1320 and 1330 is positioned onopposite sides of their corresponding pinch regions 1312, 1314 andperpendicular to passageway 1310, and are individually controllable bycontroller 210 to open and close, that is allow or prohibit fluidcommunication across the pinch regions. Thus, for example, when pinchvalve pinchers 1320 (or 1330) are brought sufficiently close, each partof pinch region 1312 (or 1314) touches another part of the pinch regionand fluid may not flow across the pinch region.

As an example of the use of pinch valve 1300, FIG. 13B shows the firstand second pair of pinch valve pinchers 1320, 1330 in an openconfiguration. FIG. 13C is a sectional view showing the pair of pinchvalve pinchers 1320 brought together, thus closing off a portion offirst leg 1311 from the second and third legs 1313, 1315. In part as aresult of the distance between pinchers 1320 and intersection 1317 thereis a volume 1321 associated with first leg 1311 that is not isolated(“dead space”). It is preferred that dead space is minimized so thatfluids of different types can be switched between the various legs ofthe pinch valve. In one embodiment, the dead space is reduced by placingthe placing the pinch valves close to the intersection of the legs. Inanother embodiment, the dead space is reduced by having passageway wallsof varying thickness. Thus, for example, excess material between thepinch valves and the intersection will more effectively isolate a valvedleg by displacing a portion of volume 1321.

As an example of the use of pinch valve 1300 in sampling system 300,pinchers 1320 and 1330 are positioned to act as valve 323 and 326,respectively.

FIGS. 14A and 14B are various views of a second embodiment pinch valve1400, where FIG. 14A is a front view and FIG. 14B is a sectional viewshowing one valve in a closed position. Pinch valve 1400 differs frompinch valve 1300 in that the pairs of pinch valve pinchers 1320 and 1330are replaced by pinchers 1420 and 1430, respectively, that are alignedwith passageway 1310.

Alternative embodiment of pinch valves includes 2, 3, 4, or morepassageway segments that meet at a common junction, with pincherslocated at one or more passageways near the junction.

FIGS. 11 and 12 illustrate various embodiment of connector 230 which mayalso form or be attached to disposable portions of cassette 820 as oneembodiment of an arterial patient connector 1100 and one embodiment avenous patient connector 1200. Connectors 1100 and 1200 may be generallysimilar to the embodiment illustrated in FIGS. 1-10, except as furtherdetailed below.

As shown in FIG. 11, arterial patient connector 1100 includes a stopcock1101, a first tube portion 1103 having a length X, a blood sampling port1105 to acquire blood samples for laboratory analysis, and fluidhandling and analysis apparatus 140, a second tube 1107 having a lengthY, and a tube connector 1109. Arterial patient connector 1100 alsoincludes a pressure sensor unit 1102 that is generally similar topressure sensor unit 1011, on the opposite side of sampling assembly220. Length X is preferably from to 6 inches (0.15 meters) to 50 inches(1.27 meters) or approximately 48 inches (1.2 meters) in length. LengthY is preferably from 1 inch (25 millimeters) to 20 inches (0.5 meters),or approximately 12 inches (0.3 meters) in length. As shown in FIG. 12,venous patient connector 1200 includes a clamp 1201, injection port1105, and tube connector 1109.

Section IV—Sample Analysis System

In several embodiments, analysis is performed on blood plasma. For suchembodiments, the blood plasma must be separated from the whole bloodobtained from the patient. In general, blood plasma may be obtained fromwhole blood at any point in fluid handling system 10 between when theblood is drawn, for example at patient connector 110 or along passageway113, and when it is analyzed. For systems where measurements arepreformed on whole blood, it may not be necessary to separate the bloodat the point of or before the measurements is performed.

For illustrative purposes, this section describes several embodiments ofseparators and analyte detection systems which may form part of system10. The separators discussed in the present specification can, incertain embodiments, comprise fluid component separators. As usedherein, the term “fluid component separator” is a broad term and is usedin its ordinary sense and includes, without limitation, any device thatis operable to separate one or more components of a fluid to generatetwo or more unlike substances. For example, a fluid component separatorcan be operable to separate a sample of whole blood into plasma andnon-plasma components, and/or to separate a solid-liquid mix (e.g. asolids-contaminated liquid) into solid and liquid components. A fluidcomponent separator need not achieve complete separation between oramong the generated unlike substances. Examples of fluid componentseparators include filters, membranes, centrifuges, electrolyticdevices, or components of any of the foregoing. Fluid componentseparators can be “active” in that they are operable to separate a fluidmore quickly than is possible through the action of gravity on a static,“standing” fluid. Section IV.A below discloses a filter which can beused as a blood separator in certain embodiments of the apparatusdisclosed herein. Section IV.B below discloses an analyte detectionsystem which can be used in certain embodiments of the apparatusdisclosed herein. Section IV.C below discloses a sample element whichcan be used in certain embodiments of the apparatus disclosed herein.Section IV.D below discloses a centrifuge and sample chamber which canbe used in certain embodiments of the apparatus disclosed herein.

Section IV.A—Blood Filter

Without limitation as to the scope of the present invention, oneembodiment of sample preparation unit 332 is shown as a blood filter1500, as illustrated in FIGS. 15 and 16, where FIG. 15 is a side view ofone embodiment of a filter, and FIG. 16 is an exploded perspective viewof the filter.

As shown in the embodiment of FIG. 15, filter 1500 that includes ahousing 1501 with an inlet 1503, a first outlet 1505 and a second outlet1507. Housing 1501 contains a membrane 1509 that divides the internalvolume of housing 1501 into a first volume 1502 that include inlet 1503and first outlet 1505 and a second volume 1504. FIG. 16 shows oneembodiment of filter 1500 as including a first plate 1511 having inlet1503 and outlet 1505, a first spacer 1513 having an opening formingfirst volume 1502, a second spacer 1515 having an opening forming secondvolume 1504, and a second plate 1517 having outlet 1507.

Filter 1500 provides for a continuous filtering of blood plasma fromwhole blood. Thus, for example, when a flow of whole blood is providedat inlet 1503 and a slight vacuum is applied to the second volume 1504side of membrane 1509, the membrane filters blood cells and blood plasmapasses through second outlet 1507. Preferably, there is transverse bloodflow across the surface of membrane 1509 to prevent blood cells fromclogging filter 1500. Accordingly, in one embodiment of the inlet 1503and first outlet 1505 may be configured to provide the transverse flowacross membrane 1509.

In one embodiment, membrane 1509 is a thin and strong polymer film. Forexample, the membrane filter may be a 10 micron thick polyester orpolycarbonate film. Preferably, the membrane filter has a smoothglass-like surface, and the holes are uniform, precisely sized, andclearly defined. The material of the film may be chemically inert andhave low protein binding characteristics.

One way to manufacture membrane 1509 is with a Track Etching process.Preferably, the “raw” film is exposed to charged particles in a nuclearreactor, which leaves “tracks” in the film. The tracks may then beetched through the film, which results in holes that are precisely sizedand uniformly cylindrical. For example, GE Osmonics, Inc. (4636 SomertonRd. Trevose, Pa. 19053-6783) utilizes a similar process to manufacture amaterial that adequately serves as the membrane filter. The surface themembrane filter depicted above is a GE Osmonics Polycarbonate TE film.

As one example of the use of filter 1500, the plasma from 3 cc of bloodmay be extracted using a polycarbonate track etch film (“PCTE”) as themembrane filter. The PCTE may have a pore size of 2 μm and an effectivearea of 170 millimeter². Preferably, the tubing connected to the supply,exhaust and plasma ports has an internal diameter of 1 millimeter. Inone embodiment of a method employed with this configuration, 100 μl ofplasma can be initially extracted from the blood. After saline is usedto rinse the supply side of the cell, another 100 μl of clear plasma canbe extracted. The rate of plasma extraction in this method andconfiguration can be about 15-25 μl/min.

Using a continuous flow mechanism to extract plasma may provide severalbenefits. In one preferred embodiment, the continuous flow mechanism isreusable with multiple samples, and there is negligible sample carryoverto contaminate subsequent samples. One embodiment may also eliminatemost situations in which plugging may occur. Additionally, a preferredconfiguration provides for a low internal volume.

Additional information on filters, methods of use thereof, and relatedtechnologies may be found in U.S. Patent Application Publication No.2005/0038357, published on Feb. 17, 2005, titled SAMPLE ELEMENT WITHBARRIER MATERIAL; and U.S. patent application Ser. No. 11/122,794, filedon May 5, 2005, titled SAMPLE ELEMENT WITH SEPARATOR. The entirecontents of the above noted publication and patent application arehereby incorporated by reference herein and made a part of thisspecification.

Section IV.B—Analyte Detection System

One embodiment of analyte detection system 334, which is not meant tolimit the scope of the present invention, is shown in FIG. 17 as anoptical analyte detection system 1700. Analyte detection system 1700 isadapted to measure spectra of blood plasma. The blood plasma provided toanalyte detection system 334 may be provided by sample preparation unit332, including but not limited to a filter 1500.

Analyte detection system 1700 comprises an energy source 1720 disposedalong a major axis X of system 1700. When activated, the energy source1720 generates an energy beam E which advances from the energy source1720 along the major axis X. In one embodiment, the energy source 1720comprises an infrared source and the energy beam E comprises an infraredenergy beam.

The energy beam E passes through an optical filter 1725 also situated onthe major axis X, before reaching a probe region 1710. Probe region 1710is portion of apparatus 322 in the path of an energized beam E that isadapted to accept a material sample S. In one embodiment, as shown inFIG. 17, probe region 1710 is adapted to accept a sample element orcuvette 1730, which supports or contains the material sample S. In oneembodiment of the present invention, sample element 1730 is a portion ofpassageway 113, such as a tube or an optical cell. After passing throughthe sample element 1730 and the sample S, the energy beam E reaches adetector 1745.

As used herein, “sample element” is a broad term and is used in itsordinary sense and includes, without limitation, structures that have asample chamber and at least one sample chamber wall, but more generallyincludes any of a number of structures that can hold, support or containa material sample and that allow electromagnetic radiation to passthrough a sample held, supported or contained thereby; e.g., a cuvette,test strip, etc.

In one embodiment of the present invention, sample element 1730 forms adisposable portion of cassette 820, and the remaining portions of system1700 form portions of instrument 810, and probe region 1710 is proberegion 1002.

With further reference to FIG. 17, the detector 1745 responds toradiation incident thereon by generating an electrical signal andpassing the signal to processor 210 for analysis. Based on the signal(s)passed to it by the detector 1745, the processor computes theconcentration of the analyte(s) of interest in the sample S, and/or theabsorbance/transmittance characteristics of the sample S at one or morewavelengths or wavelength bands employed to analyze the sample. Theprocessor 210 computes the concentration(s), absorbance(s),transmittance(s), etc. by executing a data processing algorithm orprogram instructions residing within memory 212 accessible by theprocessor 210.

In the embodiment shown in FIG. 17, the filter 1725 may comprise avarying-passband filter, to facilitate changing, over time and/or duringa measurement taken with apparatus 322, the wavelength or wavelengthband of the energy beam E that may pass the filter 1725 for use inanalyzing the sample S. (In various other embodiments, the filter 1725may be omitted altogether.) Some examples of a varying-passband filterusable with apparatus 322 include, but are not limited to, a filterwheel (discussed in further detail below), an electronically tunablefilter, such as those manufactured by Aegis Semiconductor (Woburn,Mass.), a custom filter using an “Active Thin Films platform,” aFabry-Perot interferometer, such as those manufactured by ScientificSolutions, Inc. (North Chelmsford, Mass.), a custom liquid crystalFabry-Perot (LCFP) Tunable Filter, or a tunable monochrometer, such as aHORIBA (Jobin Yvon, Inc. (Edison, N.J.) H1034 type with 7-10 μm grating,or a custom designed system.

In one embodiment detection system 1700, filter 1725 comprises avarying-passband filter, to facilitate changing, over time and/or duringa measurement taken with the detection system 1700, the wavelength orwavelength band of the energy beam E that may pass the filter 25 for usein analyzing the sample S. When the energy beam E is filtered with avarying-passband filter, the absorption/transmittance characteristics ofthe sample S can be analyzed at a number of wavelengths or wavelengthbands in a separate, sequential manner. As an example, assume that it isdesired to analyze the sample S at N separate wavelengths (Wavelength 1through Wavelength N). The varying-passband filter is first operated ortuned to permit the energy beam E to pass at Wavelength 1, whilesubstantially blocking the beam E at most or all other wavelengths towhich the detector 1745 is sensitive (including Wavelengths 2-N). Theabsorption/transmittance properties of the sample S are then measured atWavelength 1, based on the beam E that passes through the sample S andreaches the detector 1745. The varying-passband filter is then operatedor tuned to permit the energy beam E to pass at Wavelength 2, whilesubstantially blocking other wavelengths as discussed above; the sampleS is then analyzed at Wavelength 2 as was done at Wavelength 1. Thisprocess is repeated until all of the wavelengths of interest have beenemployed to analyze the sample S. The collected absorption/transmittancedata can then be analyzed by the processor 210 to determine theconcentration of the analyte(s) of interest in the material sample S.The measured spectra of sample S is referred to herein in general asC_(s)(λ_(i)), that is, a wavelength dependent spectra in which C_(s) is,for example, a transmittance, an absorbance, an optical density, or someother measure of the optical properties of sample S having values at orabout a number of wavelengths λ_(i), where i ranges over the number ofmeasurements taken. The measurement C_(s)(λ_(i)) is a linear array ofmeasurements that is alternatively written as Cs_(i).

The spectral region of system 1700 depends on the analysis technique andthe analyte and mixtures of interest. For example, one useful spectralregion for the measurement of glucose in blood using absorptionspectroscopy is the mid-IR (for example, about 4 microns to about 11microns). In one embodiment system 1700, energy source 1720 produces abeam E having an output in the range of about 4 microns to about 11microns. Although water is the main contributor to the total absorptionacross this spectral region, the peaks and other structures present inthe blood spectrum from about 6.8 microns to 10.5 microns are due to theabsorption spectra of other blood components. The 4 to 11 micron regionhas been found advantageous because glucose has a strong absorption peakstructure from about 8.5 to 10 microns, whereas most other bloodconstituents have a low and flat absorption spectrum in the 8.5 to 10micron range. The main exceptions are water and hemoglobin, both ofwhich are interferents in this region.

The amount of spectral detail provided by system 1700 depends on theanalysis technique and the analyte and mixture of interest. For example,the measurement of glucose in blood by mid-IR absorption spectroscopy isaccomplished with from 11 to 25 filters within a spectral region. In oneembodiment system 1700, energy source 1720 produces a beam E having anoutput in the range of about 4 microns to about 11 microns, and filter1725 include a number of narrow band filters within this range, eachallowing only energy of a certain wavelength or wavelength band to passtherethrough. Thus, for example, one embodiment filter 1725 includes afilter wheel having 11 filters with a nominal wavelength approximatelyequal to one of the following: 3 μm, 4.06 μm, 4.6 μm, 4.9 μm, 5.25 μm,6.12 μm, 6.47 μm, 7.98 μm, 8.35 μm, 9.65 μm, and 12.2 μm.

In one embodiment, individual infrared filters of the filter wheel aremulti-cavity, narrow band dielectric stacks on germanium or sapphiresubstrates, manufactured by either OCLI (JDS Uniphase, San Jose, Calif.)or Spectrogon US, Inc. (Parsippany, N.J.). Thus, for example, eachfilter may nominally be 1 millimeter thick and 10 millimeter square. Thepeak transmission of the filter stack is typically between 50% and 70%,and the bandwidths are typically between 150 nm and 350 nm with centerwavelengths between 4 and 10 μm. Alternatively, a second blocking IRfilter is also provided in front of the individual filters. Thetemperature sensitivity is preferably <0.01% per degree C. to assist inmaintaining nearly constant measurements over environmental conditions.

In one embodiment, the detection system 1700 computes an analyteconcentration reading by first measuring the electromagnetic radiationdetected by the detector 1745 at each center wavelength, or wavelengthband, without the sample element 1730 present on the major axis X (thisis known as an “air” reading). Second, the system 1700 measures theelectromagnetic radiation detected by the detector 1745 for each centerwavelength, or wavelength band, with the material sample S present inthe sample element 1730, and the sample element and sample S in positionon the major axis X (i.e., a “wet” reading). Finally, the processor 210computes the concentration(s), absorbance(s) and/or transmittancesrelating to the sample S based on these compiled readings.

In one embodiment, the plurality of air and wet readings are used togenerate a pathlength corrected spectrum as follows. First, themeasurements are normalized to give the transmission of the sample ateach wavelength. Using both a signal and reference measurement at eachwavelength, and letting S_(i) represent the signal of detector 1745 atwavelength i and R_(i) represent the signal of the detector atwavelength i, the transmittance, T_(i) at wavelength i may computed asT_(i)=S_(i)(wet)/S_(i)(air). Optionally, the spectra may be calculatedas the optical density, OD_(i), as −Log(T_(i)). Next, the transmissionover the wavelength range of approximately 4.5 μm to approximately 5.5μm is analyzed to determine the pathlength. Specifically, since water isthe primary absorbing species of blood over this wavelength region, andsince the optical density is the product of the optical pathlength andthe known absorption coefficient of water (OD=L σ, where L is theoptical pathlength and σ is the absorption coefficient), any one of anumber of standard curve fitting procedures may be used to determine theoptical pathlength, L from the measured OD. The pathlength may then beused to determine the absorption coefficient of the sample at eachwavelength. Alternatively, the optical pathlength may be used in furthercalculations to convert absorption coefficients to optical density.

Blood samples may be prepared and analyzed by system 1700 in a varietyof configurations. In one embodiment, sample S is obtained by drawingblood, either using a syringe or as part of a blood flow system, andtransferring the blood into sample chamber 903. In another embodiment,sample S is drawn into a sample container that is a sample chamber 903adapted for insertion into system 1700.

FIG. 44 depicts another embodiment of the analyte detection system 1700,which may be generally similar to the embodiment illustrated in FIG. 17,except as further detailed below. Where possible, similar elements areidentified with identical reference numerals in the depiction of theembodiments of FIGS. 17 and 44.

The detection system 1700 shown in FIG. 44 includes a collimator 30located between source 1720 and filter 1725 and a beam sampling optics90 between the filter and sample element 1730. Filter 1725 includes aprimary filter 40 and a filter wheel assembly 4420 which can insert oneof a plurality of optical filters into energy beam E. System 1700 alsoincludes a sample detector 150 may be generally similar to sampledetector 1725, except as further detailed below.

As shown in FIG. 44, energy beam E from source 1720 passes throughcollimator 30 through which the before reaching a primary optical filter40 which is disposed downstream of a wide end 36 of the collimator 30.Filter 1725 is aligned with the source 1720 and collimator 30 on themajor axis X and is preferably configured to operate as a broadbandfilter, allowing only a selected band, e.g. between about 2.5 μm andabout 12.5 μm, of wavelengths emitted by the source 1720 to passtherethrough, as discussed below. In one embodiment, the energy source1720 comprises an infrared source and the energy beam E comprises aninfrared energy beam. One suitable energy source 1720 is the TOMA TECH™IR-50 available from HawkEye Technologies of Milford, Conn.

With further reference to FIG. 44, primary filter 40 is mounted in amask 44 so that only those portions of the energy beam E which areincident on the primary filter 40 can pass the plane of the mask-primaryfilter assembly. The primary filter 40 is generally centered on andoriented orthogonal to the major axis X and is preferably circular (in aplane orthogonal to the major axis X) with a diameter of about 8 mm. Ofcourse, any other suitable size or shape may be employed. As discussedabove, the primary filter 40 preferably operates as a broadband filter.In the illustrated embodiment, the primary filter 40 preferably allowsonly energy wavelengths between about 4 μm and about 11 μm to passtherethrough. However, other ranges of wavelengths can be selected. Theprimary filter 40 advantageously reduces the filtering burden ofsecondary optical filter(s) 60 disposed downstream of the primary filter40 and improves the rejection of electromagnetic radiation having awavelength outside of the desired wavelength band. Additionally, theprimary filter 40 can help minimize the heating of the secondaryfilter(s) 60 by the energy beam E passing therethrough. Despite theseadvantages, the primary filter 40 and/or mask 44 may be omitted inalternative embodiments of the system 1700 shown in FIG. 44.

The primary filter 40 is preferably configured to substantially maintainits operating characteristics (center wavelength, passband width) wheresome or all of the energy beam E deviates from normal incidence by acone angle of up to about twelve degrees relative to the major axis X.In further embodiments, this cone angle may be up to about 15 to 35degrees, or from about 15 degrees or 20 degrees. The primary filter 40may be said to “substantially maintain” its operating characteristicswhere any changes therein are insufficient to affect the performance oroperation of the detection system 1700 in a manner that would raisesignificant concerns for the user(s) of the system in the context inwhich the system 1700 is employed.

In the embodiment illustrated in FIG. 44, filter wheel assembly 4420includes an optical filter wheel 50 and a stepper motor 70 connected tothe filter wheel and configured to generate a force to rotate the filterwheel 50. Additionally, a position sensor 80 is disposed over a portionof the circumference of the filter wheel 50 and may be configured todetect the angular position of the filter wheel 50 and to generate acorresponding filter wheel position signal, thereby indicating whichfilter is in position on the major axis X. Alternatively, the steppermotor 70 may be configured to track or count its own rotation(s),thereby tracking the angular position of the filter wheel, and pass acorresponding position signal to the processor 210. Two suitableposition sensors are models EE-SPX302-W2A and EE-SPX402-W2A availablefrom Omron Corporation of Kyoto, Japan.

Optical filter wheel 50 is employed as a varying-passband filter, toselectively position the secondary filter(s) 60 on the major axis Xand/or in the energy beam E. The filter wheel 50 can thereforeselectively tune the wavelength(s) of the energy beam E downstream ofthe wheel 50. These wavelength(s) vary according to the characteristicsof the secondary filter(s) 60 mounted in the filter wheel 50. The filterwheel 50 positions the secondary filter(s) 60 in the energy beam E in a“one-at-a-time” fashion to sequentially vary, as discussed above, thewavelengths or wavelength bands employed to analyze the material sampleS. An alternative to filter wheel 50 is a linear filter translated by amotor (not shown). The linear filter may be, for example, a linear arrayof separate filters or a single filter with filter properties thatchange in a linear dimension.

In alternative arrangements, the single primary filter 40 depicted inFIG. 44 may be replaced or supplemented with additional primary filtersmounted on the filter wheel 50 upstream of each of the secondary filters60. As yet another alternative, the primary filter 40 could beimplemented as a primary filter wheel (not shown) to position differentprimary filters on the major axis X at different times during operationof the detection system 1700, or as a tunable filter.

The filter wheel 50, in the embodiment depicted in FIG. 45, can comprisea wheel body 52 and a plurality of secondary filters 60 disposed on thebody 52, the center of each filter being equidistant from a rotationalcenter RC of the wheel body. The filter wheel 50 is configured to rotateabout an axis which is (i) parallel to the major axis X and (ii) spacedfrom the major axis X by an orthogonal distance approximately equal tothe distance between the rotational center RC and any of the center(s)of the secondary filter(s) 60. Under this arrangement, rotation of thewheel body 52 advances each of the filters sequentially through themajor axis X, so as to act upon the energy beam E. However, depending onthe analyte(s) of interest or desired measurement speed, only a subsetof the filters on the wheel 50 may be employed in a given measurementrun. A home position notch 54 may be provided to indicate the homeposition of the wheel 50 to a position sensor 80.

In one embodiment, the wheel body 52 can be formed from molded plastic,with each of the secondary filters 60 having, for example a thickness of1 mm and a 10 mm×10 mm or a 5 mm×5 mm square configuration. Each of thefilters 60, in this embodiment of the wheel body, is axially alignedwith a circular aperture of 4 mm diameter, and the aperture centersdefine a circle of about 1.70 inches diameter, which circle isconcentric with the wheel body 52. The body 52 itself is circular, withan outside diameter of 2.00 inches.

Each of the secondary filter(s) 60 is preferably configured to operateas a narrow band filter, allowing only a selected energy wavelength orwavelength band (i.e., a filtered energy beam (Ef) to pass therethrough.As the filter wheel 50 rotates about its rotational center RC, each ofthe secondary filter(s) 60 is, in turn, disposed along the major axis Xfor a selected dwell time corresponding to each of the secondaryfilter(s) 60.

The “dwell time” for a given secondary filter 60 is the time interval,in an individual measurement run of the system 1700, during which bothof the following conditions are true: (i) the filter is disposed on themajor axis X; and (ii) the source 1720 is energized. The dwell time fora given filter may be greater than or equal to the time during which thefilter is disposed on the major axis X during an individual measurementrun. In one embodiment of the analyte detection system 1700, the dwelltime corresponding to each of the secondary filter(s) 60 is less thanabout 1 second. However, the secondary filter(s) 60 can have other dwelltimes, and each of the filter(s) 60 may have a different dwell timeduring a given measurement run.

From the secondary filter 60, the filtered energy beam (Ef) passesthrough a beam sampling optics 90, which includes a beam splitter 4400disposed along the major axis X and having a face 4400 a disposed at anincluded angle θ relative to the major axis X. The splitter 4400preferably separates the filtered energy beam (Ef) into a sample beam(Es) and a reference beam (Er).

With further reference to FIG. 44, the sample beam (Es) passes nextthrough a first lens 4410 aligned with the splitter 4400 along the majoraxis X. The first lens 4410 is configured to focus the sample beam (Es)generally along the axis X onto the material sample S. The sample S ispreferably disposed in a sample element 1730 between a first window 122and a second window 124 of the sample element 1730. The sample element1730 is further preferably removably disposed in a holder 4430, and theholder 4430 has a first opening 132 and a second opening 134 configuredfor alignment with the first window 122 and second window 124,respectively. Alternatively, the sample element 1730 and sample S may bedisposed on the major axis X without use of the holder 4430.

At least a fraction of the sample beam (Es) is transmitted through thesample S and continues onto a second lens 4440 disposed along the majoraxis X. The second lens 4440 is configured to focus the sample beam (Es)onto a sample detector 150, thus increasing the flux density of thesample beam (Es) incident upon the sample detector 150. The sampledetector 150 is configured to generate a signal corresponding to thedetected sample beam (Es) and to pass the signal to a processor 210, asdiscussed in more detail below.

Beam sampling optics 90 further includes a third lens 160 and areference detector 170. The reference beam (Er) is directed by beamsampling optics 90 from the beam splitter 4400 to a third lens 160disposed along a minor axis Y generally orthogonal to the major axis X.The third lens 160 is configured to focus the reference beam (Er) ontoreference detector 170, thus increasing the flux density of thereference beam (Er) incident upon the reference detector 170. In oneembodiment, the lenses 4410, 4440, 160 may be formed from a materialwhich is highly transmissive of infrared radiation, for examplegermanium or silicon. In addition, any of the lenses 4410, 4440 and 160may be implemented as a system of lenses, depending on the desiredoptical performance. The reference detector 170 is also configured togenerate a signal corresponding to the detected reference beam (Er) andto pass the signal to the processor 210, as discussed in more detailbelow. Except as noted below, the sample and reference detectors 150,170 may be generally similar to the detector 1745 illustrated in FIG.17. Based on signals received from the sample and reference detectors150, 170, the processor 210 computes the concentration(s),absorbance(s), transmittance(s), etc. relating to the sample S byexecuting a data processing algorithm or program instructions residingwithin the memory 212 accessible by the processor 210.

In further variations of the detection system 1700 depicted in FIG. 44,beam sampling optics 90, including the beam splitter 4400, referencedetector 170 and other structures on the minor axis Y may be omitted,especially where the output intensity of the source 1720 is sufficientlystable to obviate any need to reference the source intensity inoperation of the detection system 1700. Thus, for example, sufficientsignals may be generated by detectors 170 and 150 with one or more oflenses 4410, 4440, 160 omitted. Furthermore, in any of the embodimentsof the analyte detection system 1700 disclosed herein, the processor 210and/or memory 212 may reside partially or wholly in a standard personalcomputer (“PC”) coupled to the detection system 1700.

FIG. 46 depicts a partial cross-sectional view of another embodiment ofan analyte detection system 1700, which may be generally similar to anyof the embodiments illustrated in FIGS. 17, 44, and 45, except asfurther detailed below. Where possible, similar elements are identifiedwith identical reference numerals in the depiction of the embodiments ofFIGS. 17, 44, and 45.

The energy source 1720 of the embodiment of FIG. 46 preferably comprisesan emitter area 22 which is substantially centered on the major axis X.In one embodiment, the emitter area 22 may be square in shape. Howeverthe emitter area 22 can have other suitable shapes, such as rectangular,circular, elliptical, etc. One suitable emitter area 22 is a square ofabout 1.5 mm on a side; of course, any other suitable shape ordimensions may be employed.

The energy source 1720 is preferably configured to selectably operate ata modulation frequency between about 1 Hz and 30 Hz and have a peakoperating temperature of between about 1070 degrees Kelvin and 1170degrees Kelvin. Additionally, the source 1720 preferably operates with amodulation depth greater than about 80% at all modulation frequencies.The energy source 1720 preferably emits electromagnetic radiation in anyof a number of spectral ranges, e.g., within infrared wavelengths; inthe mid-infrared wavelengths; above about 0.8 μm; between about 5.0 μmand about 20.0 μm and/or between about 5.25 μm and about 12.0 μm.However, in other embodiments, the detection system 1700 may employ anenergy source 1720 which is unmodulated and/or which emits inwavelengths found anywhere from the visible spectrum through themicrowave spectrum, for example anywhere from about 0.4 μm to greaterthan about 100 μm. In still other embodiments, the energy source 1720can emit electromagnetic radiation in wavelengths between about 3.5 μmand about 14 μm, or between about 0.8 μm and about 2.5 μm, or betweenabout 2.5 μm and 20 μm, or between about 20 μm and about 100 μm, orbetween about 6.85 μm and about 10.10 μm. In yet other embodiments, theenergy source 1720 can emit electromagnetic radiation within the radiofrequency (RF) range or the terahertz range. All of the above-recitedoperating characteristics are merely exemplary, and the source 1720 mayhave any operating characteristics suitable for use with the analytedetection system 1700.

A power supply (not shown) for the energy source 1720 is preferablyconfigured to selectably operate with a duty cycle of between about 30%and about 70%. Additionally, the power supply is preferably configuredto selectably operate at a modulation frequency of about 10 Hz, orbetween about 1 Hz and about 30 Hz. The operation of the power supplycan be in the form of a square wave, a sine wave, or any other waveformdefined by a user.

With further reference to FIG. 46, the collimator 30 comprises a tube 30a with one or more highly-reflective inner surfaces 32 which divergefrom a relatively narrow upstream end 34 to a relatively wide downstreamend 36 as they extend downstream, away from the energy source 1720. Thenarrow end 34 defines an upstream aperture 34 a which is situatedadjacent the emitter area 22 and permits radiation generated by theemitter area to propagate downstream into the collimator. The wide end36 defines a downstream aperture 36 a. Like the emitter area 22, each ofthe inner surface(s) 32, upstream aperture 34 a and downstream aperture36 a is preferably substantially centered on the major axis X.

As illustrated in FIG. 46, the inner surface(s) 32 of the collimator mayhave a generally curved shape, such as a parabolic, hyperbolic,elliptical or spherical shape. One suitable collimator 30 is a compoundparabolic concentrator (CPC). In one embodiment, the collimator 30 canbe up to about 20 mm in length. In another embodiment, the collimator 30can be up to about 30 mm in length. However, the collimator 30 can haveany length, and the inner surface(s) 32 may have any shape, suitable foruse with the analyte detection system 1700.

The inner surfaces 32 of the collimator 30 cause the rays making up theenergy beam E to straighten (i.e., propagate at angles increasinglyparallel to the major axis X) as the beam E advances downstream, so thatthe energy beam E becomes increasingly or substantially cylindrical andoriented substantially parallel to the major axis X. Accordingly, theinner surfaces 32 are highly reflective and minimally absorptive in thewavelengths of interest, such as infrared wavelengths.

The tube 30 a itself may be fabricated from a rigid material such asaluminum, steel, or any other suitable material, as long as the innersurfaces 32 are coated or otherwise treated to be highly reflective inthe wavelengths of interest. For example, a polished gold coating may beemployed. Preferably, the inner surface(s) 32 of the collimator 30define a circular cross-section when viewed orthogonal to the major axisX; however, other cross-sectional shapes, such as a square or otherpolygonal shapes, parabolic or elliptical shapes may be employed inalternative embodiments.

As noted above, the filter wheel 50 shown in FIG. 46 comprises aplurality of secondary filters 60 which preferably operate as narrowband filters, each filter allowing only energy of a certain wavelengthor wavelength band to pass therethrough. In one configuration suitablefor detection of glucose in a sample S, the filter wheel 50 comprisestwenty or twenty-two secondary filters 60, each of which is configuredto allow a filtered energy beam (Ef) to travel therethrough with anominal wavelength approximately equal to one of the following: 3 μm,4.06 μm, 4.6 μm, 4.9 μm, 5.25 μm, 6.12 μm, 6.47 μm, 7.98 μm, 8.35 μm,9.65 μm, and 12.2 μm. (Moreover, this set of wavelengths may be employedwith or in any of the embodiments of the analyte detection system 1700disclosed herein.) Each secondary filter's 60 center wavelength ispreferably equal to the desired nominal wavelength plus or minus about2%. Additionally, the secondary filters 60 are preferably configured tohave a bandwidth of about 0.2 μm, or alternatively equal to the nominalwavelength plus or minus about 2%-10%.

In another embodiment, the filter wheel 50 comprises twenty secondaryfilters 60, each of which is configured to allow a filtered energy beam(Ef) to travel therethrough with a nominal center wavelengths of: 4.275μm, 4.5 μm, 4.7 μm, 5.0 μm, 5.3 μm, 6.056 μm, 7.15 μm, 7.3 μm, 7.55 μm,7.67 μm, 8.06 μm, 8.4 μm, 8.56 μm, 8.87 μm, 9.15 μm, 9.27 μm, 9.48 μm,9.68 μm, 9.82 μm, and 10.06 μm. (This set of wavelengths may also beemployed with or in any of the embodiments of the analyte detectionsystem 1700 disclosed herein.) In still another embodiment, thesecondary filters 60 may conform to any one or combination of thefollowing specifications: center wavelength tolerance of ±0.01 μm;half-power bandwidth tolerance of ±0.01 μm; peak transmission greaterthan or equal to 75%; cut-on/cut-off slope less than 2%;center-wavelength temperature coefficient less than 0.01% per degreeCelsius; out of band attenuation greater than OD 5 from 3 μm to 12 μm;flatness less than 1.0 waves at 0.6328 μm; surface quality of E-E perMil-F-48616; and overall thickness of about 1 mm.

In still another embodiment, the secondary filters mentioned above mayconform to any one or combination of the following half-power bandwidth(“HPBW”) specifications:

Center Wavelength HPBW (μm) (μm) 4.275 0.05 4.5 0.18 4.7 0.13 5.0 0.15.3 0.13 6.056 0.135 7.15 0.19 7.3 0.19 7.55 0.18 7.67 0.197 8.06 0.38.4 0.2 8.56 0.18 8.87 0.2 9.15 0.15 9.27 0.14 9.48 0.23 9.68 0.3 9.820.34 10.06 0.2

In still further embodiments, the secondary filters may have a centerwavelength tolerance of ±0.5% and a half-power bandwidth tolerance of±0.02 μm.

Of course, the number of secondary filters employed, and the centerwavelengths and other characteristics thereof, may vary in furtherembodiments of the system 1700, whether such further embodiments areemployed to detect glucose, or other analytes instead of or in additionto glucose. For example, in another embodiment, the filter wheel 50 canhave fewer than fifty secondary filters 60. In still another embodiment,the filter wheel 50 can have fewer than twenty secondary filters 60. Inyet another embodiment, the filter wheel 50 can have fewer than tensecondary filters 60.

In one embodiment, the secondary filters 60 each measure about 10 mmlong by 10 mm wide in a plane orthogonal to the major axis X, with athickness of about 1 mm. However, the secondary filters 60 can have anyother (e.g., smaller) dimensions suitable for operation of the analytedetection system 1700. Additionally, the secondary filters 60 arepreferably configured to operate at a temperature of between about 5° C.and about 35° C. and to allow transmission of more than about 75% of theenergy beam E therethrough in the wavelength(s) which the filter isconfigured to pass.

According to the embodiment illustrated in FIG. 46, the primary filter40 operates as a broadband filter and the secondary filters 60 disposedon the filter wheel 50 operate as narrow band filters. However, one ofordinary skill in the art will realize that other structures can be usedto filter energy wavelengths according to the embodiments describedherein. For example, the primary filter 40 may be omitted and/or anelectronically tunable filter or Fabry-Perot interferometer (not shown)can be used in place of the filter wheel 50 and secondary filters 60.Such a tunable filter or interferometer can be configured to permit, ina sequential, “one-at-a-time” fashion, each of a set of wavelengths orwavelength bands of electromagnetic radiation to pass therethrough foruse in analyzing the material sample S.

A reflector tube 98 is preferably positioned to receive the filteredenergy beam (Ef) as it advances from the secondary filter(s) 60. Thereflector tube 98 is preferably secured with respect to the secondaryfilter(s) 60 to substantially prevent introduction of strayelectromagnetic radiation, such as stray light, into the reflector tube98 from outside of the detection system 1700. The inner surfaces of thereflector tube 98 are highly reflective in the relevant wavelengths andpreferably have a cylindrical shape with a generally circularcross-section orthogonal to the major and/or minor axis X, Y. However,the inner surface of the tube 98 can have a cross-section of anysuitable shape, such as oval, square, rectangular, etc. Like thecollimator 30, the reflector tube 98 may be formed from a rigid materialsuch as aluminum, steel, etc., as long as the inner surfaces are coatedor otherwise treated to be highly reflective in the wavelengths ofinterest. For example, a polished gold coating may be employed.

According to the embodiment illustrated in FIG. 46, the reflector tube98 preferably comprises a major section 98 a and a minor section 98 b.As depicted, the reflector tube 98 can be T-shaped with the majorsection 98 a having a greater length than the minor section 98 b. Inanother example, the major section 98 a and the minor section 98 b canhave the same length. The major section 98 a extends between a first end98 c and a second end 98 d along the major axis X. The minor section 98b extends between the major section 98 a and a third end 98 e along theminor axis Y.

The major section 98 a conducts the filtered energy beam (Ef) from thefirst end 98 c to the beam splitter 4400, which is housed in the majorsection 98 a at the intersection of the major and minor axes X, Y. Themajor section 98 a also conducts the sample beam (Es) from the beamsplitter 4400, through the first lens 4410 and to the second end 98 d.From the second end 98 d the sample beam (Es) proceeds through thesample element 1730, holder 4430 and second lens 4440, and to the sampledetector 150. Similarly, the minor section 98 b conducts the referencebeam (Er) through beam sampling optics 90 from the beam splitter 4400,through the third lens 160 and to the third end 98 e. From the third end98 e the reference beam (Er) proceeds to the reference detector 170.

The sample beam (Es) preferably comprises from about 75% to about 85% ofthe energy of the filtered energy beam (Ef). More preferably, the samplebeam (Es) comprises about 80% of the energy of the filtered energy beam(Es). The reference beam (Er) preferably comprises from about 10% andabout 50% of the energy of the filtered energy beam (Es). Morepreferably, the reference beam (Er) comprises about 20% of the energy ofthe filtered energy beam (Ef). Of course, the sample and reference beamsmay take on any suitable proportions of the energy beam E.

The reflector tube 98 also houses the first lens 4410 and the third lens160. As illustrated in FIG. 46, the reflector tube 98 houses the firstlens 4410 between the beam splitter 4400 and the second end 98 d. Thefirst lens 4410 is preferably disposed so that a plane 4612 of the lens4410 is generally orthogonal to the major axis X. Similarly, the tube 98houses the third lens 160 between the beam splitter 4400 and the thirdend 98 e. The third lens 160 is preferably disposed so that a plane 162of the third lens 160 is generally orthogonal to the minor axis Y. Thefirst lens 4410 and the third lens 160 each has a focal lengthconfigured to substantially focus the sample beam (Es) and referencebeam (Er), respectively, as the beams (Es, Er) pass through the lenses4410, 160. In particular, the first lens 4410 is configured, anddisposed relative to the holder 4430, to focus the sample beam (Es) sothat substantially the entire sample beam (Es) passes through thematerial sample S, residing in the sample element 1730. Likewise, thethird lens 160 is configured to focus the reference beam (Er) so thatsubstantially the entire reference beam (Er) impinges onto the referencedetector 170.

The sample element 1730 is retained within the holder 4430, which ispreferably oriented along a plane generally orthogonal to the major axisX. The holder 4430 is configured to be slidably displaced between aloading position and a measurement position within the analyte detectionsystem 1700. In the measurement position, the holder 4430 contacts astop edge 136 which is located to orient the sample element 1730 and thesample S contained therein on the major axis X.

The structural details of the holder 4430 depicted in FIG. 46 areunimportant, so long as the holder positions the sample element 1730 andsample S on and substantially orthogonal to the major axis X, whilepermitting the energy beam E to pass through the sample element andsample. As with the embodiment depicted in FIG. 44, the holder 4430 maybe omitted and the sample element 1730 positioned alone in the depictedlocation on the major axis X. However, the holder 4430 is useful wherethe sample element 1730 (discussed in further detail below) isconstructed from a highly brittle or fragile material, such as bariumfluoride, or is manufactured to be extremely thin.

As with the embodiment depicted in FIG. 44, the sample and referencedetectors 150, 170 shown in FIG. 46 respond to radiation incidentthereon by generating signals and passing them to the processor 210.Based these signals received from the sample and reference detectors150, 170, the processor 210 computes the concentration(s),absorbance(s), transmittance(s), etc. relating to the sample S byexecuting a data processing algorithm or program instructions residingwithin the memory 212 accessible by the processor 210. In furthervariations of the detection system 1700 depicted in FIG. 46, the beamsplitter 4400, reference detector 170 and other structures on the minoraxis Y may be omitted, especially where the output intensity of thesource 1720 is sufficiently stable to obviate any need to reference thesource intensity in operation of the detection system 1700.

FIG. 47 depicts a sectional view of the sample detector 150 inaccordance with one embodiment. Sample detector 150 is mounted in adetector housing 152 having a receiving portion 152 a and a cover 152 b.However, any suitable structure may be used as the sample detector 150and housing 152. The receiving portion 152 a preferably defines anaperture 152 c and a lens chamber 152 d, which are generally alignedwith the major axis X when the housing 152 is mounted in the analytedetection system 1700. The aperture 152 c is configured to allow atleast a fraction of the sample beam (Es) passing through the sample Sand the sample element 1730 to advance through the aperture 152 c andinto the lens chamber 152 d.

The receiving portion 152 a houses the second lens 4440 in the lenschamber 152 d proximal to the aperture 152 c. The sample detector 150 isalso disposed in the lens chamber 152 d downstream of the second lens4440 such that a detection plane 154 of the detector 150 issubstantially orthogonal to the major axis X. The second lens 4440 ispositioned such that a plane 142 of the lens 4440 is substantiallyorthogonal to the major axis X. The second lens 4440 is configured, andis preferably disposed relative to the holder 4430 and the sampledetector 150, to focus substantially all of the sample beam (Es) ontothe detection plane 154, thereby increasing the flux density of thesample beam (Es) incident upon the detection plane 154.

With further reference to FIG. 47, a support member 156 preferably holdsthe sample detector 150 in place in the receiving portion 152 a. In theillustrated embodiment, the support member 156 is a spring 156 disposedbetween the sample detector 150 and the cover 152 b. The spring 156 isconfigured to maintain the detection plane 154 of the sample detector150 substantially orthogonal to the major axis X. A gasket 157 ispreferably disposed between the cover 152 b and the receiving portion152 a and surrounds the support member 156.

The receiving portion 152 a preferably also houses a printed circuitboard 158 disposed between the gasket 157 and the sample detector 150.The board 158 connects to the sample detector 150 through at least oneconnecting member 150 a. The sample detector 150 is configured togenerate a detection signal corresponding to the sample beam (Es)incident on the detection plane 154. The sample detector 150communicates the detection signal to the circuit board 158 through theconnecting member 150 a, and the board 158 transmits the detectionsignal to the processor 210.

In one embodiment, the sample detector 150 comprises a generallycylindrical housing 150 a, e.g. a type TO-39 “metal can” package, whichdefines a generally circular housing aperture 150 b at its “upstream”end. In one embodiment, the housing 150 a has a diameter of about 0.323inches and a depth of about 0.248 inches, and the aperture 150 b mayhave a diameter of about 0.197 inches.

A detector window 150 c is disposed adjacent the aperture 150 b, withits upstream surface preferably about 0.078 inches (+/−0.004 inches)from the detection plane 154. (The detection plane 154 is located about0.088 inches (+/−0.004 inches) from the upstream edge of the housing 150a, where the housing has a thickness of about 0.010 inches.) Thedetector window 150 c is preferably transmissive of infrared energy inat least a 3-12 micron passband; accordingly, one suitable material forthe window 150 c is germanium. The endpoints of the passband may be“spread” further to less than 2.5 microns, and/or greater than 12.5microns, to avoid unnecessary absorbance in the wavelengths of interest.Preferably, the transmittance of the detector window 150 c does not varyby more than 2% across its passband. The window 150 c is preferablyabout 0.020 inches in thickness. The sample detector 150 preferablysubstantially retains its operating characteristics across a temperaturerange of −20 to +60 degrees Celsius.

FIG. 48 depicts a sectional view of the reference detector 170 inaccordance with one embodiment. The reference detector 170 is mounted ina detector housing 172 having a receiving portion 172 a and a cover 172b. However, any suitable structure may be used as the sample detector150 and housing 152. The receiving portion 172 a preferably defines anaperture 172 c and a chamber 172 d which are generally aligned with theminor axis Y, when the housing 172 is mounted in the analyte detectionsystem 1700. The aperture 172 c is configured to allow the referencebeam (Er) to advance through the aperture 172 c and into the chamber 172d.

The receiving portion 172 a houses the reference detector 170 in thechamber 172 d proximal to the aperture 172 c. The reference detector 170is disposed in the chamber 172 d such that a detection plane 174 of thereference detector 170 is substantially orthogonal to the minor axis Y.The third lens 160 is configured to substantially focus the referencebeam (Er) so that substantially the entire reference beam (Er) impingesonto the detection plane 174, thus increasing the flux density of thereference beam (Er) incident upon the detection plane 174.

With further reference to FIG. 48, a support member 176 preferably holdsthe reference detector 170 in place in the receiving portion 172 a. Inthe illustrated embodiment, the support member 176 is a spring 176disposed between the reference detector 170 and the cover 172 b. Thespring 176 is configured to maintain the detection plane 174 of thereference detector 170 substantially orthogonal to the minor axis Y. Agasket 177 is preferably disposed between the cover 172 b and thereceiving portion 172 a and surrounds the support member 176.

The receiving portion 172 a preferably also houses a printed circuitboard 178 disposed between the gasket 177 and the reference detector170. The board 178 connects to the reference detector 170 through atleast one connecting member 170 a. The reference detector 170 isconfigured to generate a detection signal corresponding to the referencebeam (Er) incident on the detection plane 174. The reference detector170 communicates the detection signal to the circuit board 178 throughthe connecting member 170 a, and the board 178 transmits the detectionsignal to the processor 210.

In one embodiment, the construction of the reference detector 170 isgenerally similar to that described above with regard to the sampledetector 150.

In one embodiment, the sample and reference detectors 150, 170 are bothconfigured to detect electromagnetic radiation in a spectral wavelengthrange of between about 0.8 μm and about 25 μm. However, any suitablesubset of the foregoing set of wavelengths can be selected. In anotherembodiment, the detectors 150, 170 are configured to detectelectromagnetic radiation in the wavelength range of between about 4 μmand about 12 μm. The detection planes 154, 174 of the detectors 150, 170may each define an active area about 2 mm by 2 mm or from about 1 mm by1 mm to about 5 mm by 5 mm; of course, any other suitable dimensions andproportions may be employed. Additionally, the detectors 150, 170 may beconfigured to detect electromagnetic radiation directed thereto within acone angle of about 45 degrees from the major axis X.

In one embodiment, the sample and reference detector subsystems 150, 170may further comprise a system (not shown) for regulating the temperatureof the detectors. Such a temperature-regulation system may comprise asuitable electrical heat source, thermistor, and aproportional-plus-integral-plus-derivative (PID) control. Thesecomponents may be used to regulate the temperature of the detectors 150,170 at about 35° C. The detectors 150, 170 can also optionally beoperated at other desired temperatures. Additionally, the PID controlpreferably has a control rate of about 60 Hz and, along with the heatsource and thermistor, maintains the temperature of the detectors 150,170 within about 0.1° C. of the desired temperature.

The detectors 150, 170 can operate in either a voltage mode or a currentmode, wherein either mode of operation preferably includes the use of apre-amp module. Suitable voltage mode detectors for use with the analytedetection system 1700 disclosed herein include: models LIE 302 and 312by InfraTec of Dresden, Germany; model L2002 by BAE Systems ofRockville, Md.; and model LTS-1 by Dias of Dresden, Germany. Suitablecurrent mode detectors include: InfraTec models LIE 301, 315, 345 and355; and 2×2 current-mode detectors available from Dias.

In one embodiment, one or both of the detectors 150, 170 may meet thefollowing specifications, when assuming an incident radiation intensityof about 9.26×10⁻⁴ watts (rms) per cm², at 10 Hz modulation and within acone angle of about 15 degrees: detector area of 0.040 cm² (2mm×2 mmsquare); detector input of 3.70×10⁻⁵ watts (rms) at 10 Hz; detectorsensitivity of 360 volts per watt at 10 Hz; detector output of1.333×10⁻² volts (rms) at 10 Hz; noise of 8.00×10⁻⁸ volts/sqrtHz at 10Hz; and signal-to-noise ratios of 1.67×10⁵ rms/sqrtHz and 104.4dB/sqrtHz; and detectivity of 1.00×10⁹ cm sqrtHz/watt.

In alternative embodiments, the detectors 150, 170 may comprisemicrophones and/or other sensors suitable for operation of the detectionsystem 1700 in a photoacoustic mode.

The components of any of the embodiments of the analyte detection system1700 may be partially or completely contained in an enclosure or casing(not shown) to prevent stray electromagnetic radiation, such as straylight, from contaminating the energy beam E. Any suitable casing may beused. Similarly, the components of the detection system 1700 may bemounted on any suitable frame or chassis (not shown) to maintain theiroperative alignment as depicted in FIGS. 17, 44, and 46. The frame andthe casing may be formed together as a single unit, member or collectionof members.

In one method of operation, the analyte detection system 1700 shown inFIG. 44 or 46 measures the concentration of one or more analytes in thematerial sample S, in part, by comparing the electromagnetic radiationdetected by the sample and reference detectors 150, 170. Duringoperation of the detection system 1700, each of the secondary filter(s)60 is sequentially aligned with the major axis X for a dwell timecorresponding to the secondary filter 60. (Of course, where anelectronically tunable filter or Fabry-Perot interferometer is used inplace of the filter wheel 50, the tunable filter or interferometer issequentially tuned to each of a set of desired wavelengths or wavelengthbands in lieu of the sequential alignment of each of the secondaryfilters with the major axis X.) The energy source 1720 is then operatedat (any) modulation frequency, as discussed above, during the dwell timeperiod. The dwell time may be different for each secondary filter 60 (oreach wavelength or band to which the tunable filter or interferometer istuned). In one embodiment of the detection system 1700, the dwell timefor each secondary filter 60 is less than about 1 second. Use of a dwelltime specific to each secondary filter 60 advantageously allows thedetection system 1700 to operate for a longer period of time atwavelengths where errors can have a greater effect on the computation ofthe analyte concentration in the material sample S. Correspondingly, thedetection system 1700 can operate for a shorter period of time atwavelengths where errors have less effect on the computed analyteconcentration. The dwell times may otherwise be nonuniform among thefilters/wavelengths/bands employed in the detection system.

For each secondary filter 60 selectively aligned with the major axis X,the sample detector 150 detects the portion of the sample beam (Es), atthe wavelength or wavelength band corresponding to the secondary filter60, that is transmitted through the material sample S. The sampledetector 150 generates a detection signal corresponding to the detectedelectromagnetic radiation and passes the signal to the processor 210.Simultaneously, the reference detector 170 detects the reference beam(Er) transmitted at the wavelength or wavelength band corresponding tothe secondary filter 60. The reference detector 170 generates adetection signal corresponding to the detected electromagnetic radiationand passes the signal to the processor 210. Based on the signals passedto it by the detectors 150, 170, the processor 210 computes theconcentration of the analyte(s) of interest in the sample S, and/or theabsorbance/transmittance characteristics of the sample S at one or morewavelengths or wavelength bands employed to analyze the sample. Theprocessor 210 computes the concentration(s), absorbance(s),transmittance(s), etc. by executing a data processing algorithm orprogram instructions residing within the memory 212 accessible by theprocessor 210.

The signal generated by the reference detector may be used to monitorfluctuations in the intensity of the energy beam emitted by the source1720, which fluctuations often arise due to drift effects, aging, wearor other imperfections in the source itself. This enables the processor210 to identify changes in intensity of the sample beam (Es) that areattributable to changes in the emission intensity of the source 1720,and not to the composition of the sample S. By so doing, a potentialsource of error in computations of concentration, absorbance, etc. isminimized or eliminated.

In one embodiment, the detection system 1700 computes an analyteconcentration reading by first measuring the electromagnetic radiationdetected by the detectors 150, 170 at each center wavelength, orwavelength band, without the sample element 1730 present on the majoraxis X (this is known as an “air” reading). Second, the system 1700measures the electromagnetic radiation detected by the detectors 150,170 for each center wavelength, or wavelength band, with the materialsample S present in the sample element 1730, and the sample element 1730and sample S in position on the major axis X (i.e., a “wet” reading).Finally, the processor 180 computes the concentration(s), absorbance(s)and/or transmittances relating to the sample S based on these compiledreadings.

In one embodiment, the plurality of air and wet readings are used togenerate a pathlength corrected spectrum as follows. First, themeasurements are normalized to give the transmission of the sample ateach wavelength. Using both a signal and reference measurement at eachwavelength, and letting S_(i) represent the signal of detector 150 atwavelength i and R_(i) represent the signal of detector 170 atwavelength i, the transmission, τ_(i) is computed asτ_(i)=S_(i)(wet)/R_(i)(wet)/S_(i)(air)/R_(i)(air). Optionally, thespectra may be calculated as the optical density, OD_(i), as−Log(T_(i)).

Next, the transmission over the wavelength range of approximately 4.5 μmto approximately 5.5 μm is analyzed to determine the pathlength.Specifically, since water is the primary absorbing species of blood overthis wavelength region, and since the optical density is the product ofthe optical pathlength and the known absorption coefficient of water(OD=L σ, where L is the optical pathlength and σ is the absorptioncoefficient), any one of a number of standard curve fitting proceduresmay be used to determine the optical pathlength, L from the measured OD.The pathlength may then be used to determine the absorption coefficientof the sample at each wavelength. Alternatively, the optical pathlengthmay be used in further calculations to convert absorption coefficientsto optical density.

Additional information on analyte detection systems, methods of usethereof, and related technologies may be found in the above-mentionedand incorporated U.S. Patent Application Publication No. 2005/0038357,published on Feb. 17, 2005, titled SAMPLE ELEMENT WITH BARRIER MATERIAL.

Section IV.C—Sample Element

FIG. 18 is a top view of a sample element 1730, FIG. 19 is a side viewof the sample element, and FIG. 20 is an exploded perspective view ofthe sample element. In one embodiment of the present invention, sampleelement 1730 includes sample chamber 903 that is in fluid communicationwith and accepts filtered blood from sample preparation unit 332. Thesample element 1730 comprises a sample chamber 903 defined by samplechamber walls 1802. The sample chamber 903 is configured to hold amaterial sample which may be drawn from a patient, for analysis by thedetection system with which the sample element 1730 is employed.

In the embodiment illustrated in FIGS. 18-19, the sample chamber 903 isdefined by first and second lateral chamber walls 1802 a, 1802 b andupper and lower chamber walls 1802 c, 1802 d; however, any suitablenumber and configuration of chamber walls may be employed. At least oneof the upper and lower chamber walls 1802 c, 1802 d is formed from amaterial which is sufficiently transmissive of the wavelength(s) ofelectromagnetic radiation that are employed by the sample analysisapparatus 322 (or any other system with which the sample element is tobe used). A chamber wall which is so transmissive may thus be termed a“window;” in one embodiment, the upper and lower chamber walls 1802 c,1802 d comprise first and second windows so as to permit the relevantwavelength(s) of electromagnetic radiation to pass through the samplechamber 903. In another embodiment, only one of the upper and lowerchamber walls 1802 c, 1802 d comprises a window; in such an embodiment,the other of the upper and lower chamber walls may comprise a reflectivesurface configured to back-reflect any electromagnetic energy emittedinto the sample chamber 903 by the analyte detection system with whichthe sample element 1730 is employed. Accordingly, this embodiment iswell suited for use with an analyte detection system in which a sourceand a detector of electromagnetic energy are located on the same side asthe sample element.

In various embodiments, the material that makes up the window(s) of thesample element 1730 is completely transmissive, i.e., it does not absorbany of the electromagnetic radiation from the source 1720 and filters1725 that is incident upon it. In another embodiment, the material ofthe window(s) has some absorption in the electromagnetic range ofinterest, but its absorption is negligible. In yet another embodiment,the absorption of the material of the window(s) is not negligible, butit is stable for a relatively long period of time. In anotherembodiment, the absorption of the window(s) is stable for only arelatively short period of time, but sample analysis apparatus 322 isconfigured to observe the absorption of the material and eliminate itfrom the analyte measurement before the material properties can changemeasurably. Materials suitable for forming the window(s) of the sampleelement 1730 include, but are not limited to, calcium fluoride, bariumfluoride, germanium, silicon, polypropylene, polyethylene, or anypolymer with suitable transmissivity (i.e., transmittance per unitthickness) in the relevant wavelength(s). Where the window(s) are formedfrom a polymer, the selected polymer can be isotactic, atactic orsyndiotactic in structure, so as to enhance the flow of the samplebetween the window(s). One type of polyethylene suitable forconstructing the sample element 1730 is type 220, extruded or blowmolded, available from KUBE Ltd. of Staefa, Switzerland.

In one embodiment, the sample element 1730 is configured to allowsufficient transmission of electromagnetic energy having a wavelength ofbetween about 4 μm and about 10.5 μm through the window(s) thereof.However, the sample element 1730 can be configured to allow transmissionof wavelengths in any spectral range emitted by the energy source 1720.In another embodiment, the sample element 1730 is configured to receivean optical power of more than about 1.0 MW/cm² from the sample beam (Es)incident thereon for any electromagnetic radiation wavelengthtransmitted through the filter 1725. Preferably, the sample chamber 903of the sample element 1730 is configured to allow a sample beam (Es)advancing toward the material sample S within a cone angle of 45 degreesfrom the major axis X (see FIG. 17) to pass therethrough.

In the embodiment illustrated in FIGS. 18-19, the sample element furthercomprises a supply passage 1804 extending from the sample chamber 903 toa supply opening 1806 and a vent passage 1808 extending from the samplechamber 903 to a vent opening 1810. While the vent and supply openings1806, 1810 are shown at one end of the sample element 1730, in otherembodiments the openings may be positioned on other sides of the sampleelement 1730, so long as it is in fluid communication with the passages1804 and 1808, respectively.

In operation, the supply opening 1806 of the sample element 1730 isplaced in contact with the material sample S, such as a fluid flowingfrom a patient. The fluid is then transported through the sample supplypassage 1804 and into the sample chamber 903 via an external pump or bycapillary action.

Where the upper and lower chamber walls 1802 c, 1802 d comprise windows,the distance T (measured along an axis substantially orthogonal to thesample chamber 903 and/or windows 1802 a, 1802 b, or, alternatively,measured along an axis of an energy beam (such as but not limited to theenergy beam E discussed above) passed through the sample chamber 903 )between them comprises an optical pathlength. In various embodiments,the pathlength is between about 1 μm and about 300 μm, between about 1μm and about 100 μm, between about 25 μm and about 40 μm, between about10 μm and about 40 μm, between about 25 μm and about 60 μm, or betweenabout 30 μm and about 50 μm. In still other embodiments, the opticalpathlength is about 50 μm, or about 25 μm. In some instances, it isdesirable to hold the pathlength T to within about plus or minus 1 μmfrom any pathlength specified by the analyte detection system with whichthe sample element 1730 is to be employed. Likewise, it may be desirableto orient the walls 1802 c, 1802 d with respect to each other withinplus or minus 1 μm of parallel, and/or to maintain each of the walls1802 c, 1802 d to within plus or minus 1 μm of planar (flat), dependingon the analyte detection system with which the sample element 1730 is tobe used. In alternative embodiments, walls 1802 c, 1802 d are flat,textured, angled, or some combination thereof.

In one embodiment, the transverse size of the sample chamber 903 (i.e.,the size defined by the lateral chamber walls 1802 a, 1802 b) is aboutequal to the size of the active surface of the sample detector 1745.Accordingly, in a further embodiment the sample chamber 903 is roundwith a diameter of about 4 millimeter to about 12 millimeter, and morepreferably from about 6 millimeter to about 8 millimeter.

The sample element 1730 shown in FIGS. 18-19 has, in one embodiment,sizes and dimensions specified as follows. The supply passage 1804preferably has a length of about 15 millimeter, a width of about 1.0millimeter, and a height equal to the pathlength T. Additionally, thesupply opening 1806 is preferably about 1.5 millimeter wide and smoothlytransitions to the width of the sample supply passage 1804. The sampleelement 1730 is about 0.5 inches (12 millimeters) wide and about oneinch (25 millimeters) long with an overall thickness of between about1.0 millimeter and about 4.0 millimeter. The vent passage 1808preferably has a length of about 1.0 millimeter to 5.0 millimeter and awidth of about 1.0 millimeter, with a thickness substantially equal tothe pathlength between the walls 1802 c, 1802 d. The vent aperture 1810is of substantially the same height and width as the vent passage 1808.Of course, other dimensions may be employed in other embodiments whilestill achieving the advantages of the sample element 1730.

The sample element 1730 is preferably sized to receive a material sampleS having a volume less than or equal to about 15 μL (or less than orequal to about 10 μL, or less than or equal to about 5 μL) and morepreferably a material sample S having a volume less than or equal toabout 2 μL. Of course, the volume of the sample element 1730, the volumeof the sample chamber 903, etc. can vary, depending on many variables,such as the size and sensitivity of the sample detector 1745, theintensity of the radiation emitted by the energy source 1720, theexpected flow properties of the sample, and whether flow enhancers areincorporated into the sample element 1730. The transport of fluid to thesample chamber 903 is achieved preferably through capillary action, butmay also be achieved through wicking or vacuum action, or a combinationof wicking, capillary action, peristaltic, pumping, and/or vacuumaction.

FIG. 20 depicts one approach to constructing the sample element 1730. Inthis approach, the sample element 1730 comprises a first layer 1820, asecond layer 1830, and a third layer 1840. The second layer 1830 ispreferably positioned between the first layer 1820 and the third layer1840. The first layer 1820 forms the upper chamber wall 1802 c, and thethird layer 1840 forms the lower chamber wall 1802 d. Where either ofthe chamber walls 1802 c, 1802 d comprises a window, thewindow(s)/wall(s) 1802 c/1802 d in question may be formed from adifferent material as is employed to form the balance of the layer(s)1820/1840 in which the wall(s) are located. Alternatively, the entiretyof the layer(s) 1820/1840 may be formed of the material selected to formthe window(s)/wall(s) 1802 c, 1802 d. In this case, thewindow(s)/wall(s) 1802 c, 1802 d are integrally formed with the layer(s)1820, 1840 and simply comprise the regions of the respective layer(s)1820, 1840 which overlie the sample chamber 903.

With further reference to FIG. 20, second layer 1830 may be formedentirely of an adhesive that joins the first and third layers 1820,1840. In other embodiments, the second layer 1830 may be formed fromsimilar materials as the first and third layers, or any other suitablematerial. The second layer 1830 may also be formed as a carrier with anadhesive deposited on both sides thereof. The second layer 1830 includesvoids which at least partially form the sample chamber 903, samplesupply passage 1804, supply opening 1806, vent passage 1808, and ventopening 1810. The thickness of the second layer 1830 can be the same asany of the pathlengths disclosed above as suitable for the sampleelement 1730. The first and third layers can be formed from any of thematerials disclosed above as suitable for forming the window(s) of thesample element 1730. In one embodiment, layers 1820, 1840 are formedfrom material having sufficient structural integrity to maintain itsshape when filled with a sample S. Layers 1820, 1830 may be, forexample, calcium fluoride having a thickness of 0.5 millimeter. Inanother embodiment, the second layer 1830 comprises the adhesive portionof Adhesive Transfer Tape no. 9471LE available from 3M Corporation. Inanother embodiment, the second layer 1830 comprises an epoxy, available,for example, from TechFilm (31 Dunham Road, Billerica, Mass. 01821),that is bound to layers 1820, 1840 as a result of the application ofpressure and heat to the layers.

The sample chamber 903 preferably comprises a reagentless chamber. Inother words, the internal volume of the sample chamber 903 and/or thewall(s) 1802 defining the chamber 903 are preferably inert with respectto the sample to be drawn into the chamber for analysis. As used herein,“inert” is a broad term and is used in its ordinary sense and includes,without limitation, substances which will not react with the sample in amanner which will significantly affect any measurement made of theconcentration of analyte(s) in the sample with sample analysis apparatus322 or any other suitable system, for a sufficient time (e.g., about1-30 minutes) following entry of the sample into the chamber 903, topermit measurement of the concentration of such analyte(s).Alternatively, the sample chamber 903 may contain one or more reagentsto facilitate use of the sample element in sample assay techniques whichinvolve reaction of the sample with a reagent.

In one embodiment of the present invention, sample element 1730 is usedfor a limited number of measurements and is disposable. Thus, forexample, with reference to FIGS. 8-10, sample element 1730 forms adisposable portion of cassette 820 adapted to place sample chamber 903within probe region 1002.

Additional information on sample elements, methods of use thereof, andrelated technologies may be found in the above-mentioned andincorporated U.S. Patent Application Publication No. 2005/0038357,published on Feb. 17, 2005, titled SAMPLE ELEMENT WITH BARRIER MATERIAL;and in the above-mentioned and incorporated U.S. patent application Ser.No. 11/122,794, filed on May 5, 2005, titled SAMPLE ELEMENT WITHSEPARATOR.

Section IV.D—Centrifuge

FIG. 21 is a schematic of one embodiment of a sample preparation unit2100 utilizing a centrifuge and which may be generally similar to thesample preparation unit 332, except as further detailed below. Ingeneral, the sample preparation unit 332 includes a centrifuge in placeof, or in addition to a filter, such as the filter 1500. Samplepreparation unit 2100 includes a fluid handling element in the form of acentrifuge 2110 having a sample element 2112 and a fluid interface 2120.Sample element 2112 is illustrated in FIG. 21 as a somewhat cylindricalelement. This embodiment is illustrative, and the sample element may becylindrical, planar, or any other shape or configuration that iscompatible with the function of holding a material (preferably a liquid)in the centrifuge 2110. The centrifuge 2110 can be used to rotate thesample element 2112 such that the material held in the sample element2112 is separated.

In some embodiments, the fluid interface 2120 selectively controls thetransfer of a sample from the passageway 113 and into the sample element2112 to permit centrifuging of the sample. In another embodiment, thefluid interface 2120 also permits a fluid to flow though the sampleelement 2112 to cleanse or otherwise prepare the sample element forobtaining an analyte measurement. Thus, the fluid interface 2120 can beused to flush and fill the sample element 2112.

As shown in FIG. 21, the centrifuge 2110 comprises a rotor 2111 thatincludes the sample element 2112 and an axle 2113 attached to a motor,not shown, which is controlled by the controller 210. The sample element2112 is preferably generally similar to the sample element 1730 exceptas described subsequently.

As is further shown in FIG. 21, fluid interface 2120 includes a fluidinjection probe 2121 having a first needle 2122 and a fluid removalprobe 2123. The fluid removal probe 2123 has a second needle 2124. Whensample element 2112 is properly oriented relative to fluid interface2120, a sample, fluid, or other liquid is dispensed into or passesthrough the sample element 2112. More specifically, fluid injectionprobe 2121 includes a passageway to receive a sample, such as a bodilyfluid from the patient connector 110. The bodily fluid can be passedthrough the fluid injection probe 2121 and the first needle 2122 intothe sample element 2112. To remove material from the sample element2112, the sample 2112 can be aligned with the second needle 2124, asillustrated. Material can be passed through the second needle 2124 intothe fluid removal probe 2123. The material can then pass through apassageway of the removal probe 2123 away from the sample element 2112.

One position that the sample element 2112 may be rotated through or tois a sample measurement location 2140. The location 2140 may coincidewith a region of an analysis system, such as an optical analytedetection system. For example, the location 2140 may coincide with aprobe region 1002, or with a measurement location of another apparatus.

The rotor 2111 may be driven in a direction indicated by arrow R,resulting in a centrifugal force on sample(s) within sample element2112. The rotation of a sample(s) located a distance from the center ofrotation creates centrifugal force. In some embodiments, the sampleelement 2112 holds whole blood. The centrifugal force may cause thedenser parts of the whole blood sample to move further out from thecenter of rotation than lighter parts of the blood sample. As such, oneor more components of the whole blood can be separated from each other.Other fluids or samples can also be removed by centrifugal forces. Inone embodiment, the sample element 2112 is a disposable container thatis mounted on to a disposable rotor 2111. Preferably, the container isplastic, reusable and flushable. In other embodiments, the sampleelement 2112 is a non-disposable container that is permanently attachedto the rotor 2111.

The illustrated rotor 2111 is a generally circular plate that is fixedlycoupled to the axle 2113. The rotor 2111 can alternatively have othershapes. The rotor 2111 preferably comprises a material that has a lowdensity to keep the rotational inertia low and that is sufficientlystrong and stable to maintain shape under operating loads to maintainclose optical alignment. For example, the rotor 2111 can be comprised ofGE brand ULTEM (trademark) polyetherimide (PEI). This material isavailable in a plate form that is stable but can be readily machined.Other materials having similar properties can also be used.

The size of the rotor 2111 can be selected to achieve the desiredcentrifugal force. In some embodiments, the diameter of rotor 2111 isfrom about 75 millimeters to about 125 millimeters, or more preferablyfrom about 100 millimeters to about 125 millimeters. The thickness ofrotor 2111 is preferably just thick enough to support the centrifugalforces and can be, for example, from about 1.0 to 2.0 millimeter thick.

In an alternative embodiment, the fluid interface 2120 selectivelyremoves blood plasma from the sample element 2112 after centrifuging.The blood plasma is then delivered to an analyte detection system foranalysis. In one embodiment, the separated fluids are removed from thesample element 2112 through the bottom connector. Preferably, thelocation and orientation of the bottom connector and the container allowthe red blood cells to be removed first. One embodiment may beconfigured with a red blood cell detector. The red blood cell detectormay detect when most of the red blood cells have exited the container bydetermining the haemostatic level. The plasma remaining in the containermay then be diverted into the analysis chamber. After the fluids havebeen removed from the container, the top connector may inject fluid(e.g., saline) into the container to flush the system and prepare it forthe next sample.

FIGS. 22A to 23C illustrate another embodiment of a fluid handling andanalysis apparatus 140, which employs a removable, disposable fluidhandling cassette 820. The cassette 820 is equipped with a centrifugerotor assembly 2016 to facilitate preparation and analysis of a sample.Except as further described below, the apparatus 140 of FIGS. 22A-22Ccan in certain embodiments be similar to any of the other embodiments ofthe apparatus 140 discussed herein, and the cassette 820 can in certainembodiments be similar to any of the embodiments of the cassettes 820disclosed herein.

The removable fluid handling cassette 820 can be removably engaged witha main analysis instrument 810. When the fluid handling cassette 820 iscoupled to the main instrument 810, a drive system 2030 of the maininstrument 810 mates with the rotor assembly 2016 of the cassette 820(FIG. 22B). Once the cassette 820 is coupled to the main instrument 810,the drive system 2030 engages and can rotate the rotor assembly 2016 toapply a centrifugal force to a body fluid sample carried by the rotorassembly 2016.

In some embodiments, the rotor assembly 2016 includes a rotor 2020sample element 2448 (FIG. 22C) for holding a sample for centrifuging.When the rotor 2020 is rotated, a centrifugal force is applied to thesample contained within the sample element 2448. The centrifugal forcecauses separation of one or more components of the sample (e.g.,separation of plasma from whole blood). The separated component(s) canthen be analyzed by the apparatus 140, as will be discussed in furtherdetail below.

The main instrument 810 includes both the centrifuge drive system 2030and an analyte detection system 1700, a portion of which protrudes froma housing 2049 of the main instrument 810. The drive system 2030 isconfigured to releasably couple with the rotor assembly 2016, and canimpart rotary motion to the rotor assembly 2016 to rotate the rotor 2020at a desired speed. After the centrifuging process, the analytedetection system 1700 can analyze one or more components separated fromthe sample carried by the rotor 2020. The projecting portion of theillustrated detection system 1700 forms a slot 2074 for receiving aportion of the rotor 2020 carrying the sample element 2448 so that thedetection system 1700 can analyze the sample or component(s) carried inthe sample element 2448.

To assemble the fluid handling and analysis apparatus 140 as shown inFIG. 22C, the cassette 820 is placed on the main instrument 810, asindicated by the arrow 2007 of FIGS. 22A and 22 B. The rotor assembly2016 is accessible to the drive system 2030, so that once the cassette820 is properly mounted on the main instrument 810, the drive system2030 is in operative engagement with the rotor assembly 2016. The drivesystem 2030 is then energized to spin the rotor 2020 at a desired speed.The spinning rotor 2020 can pass repeatedly through the slot 2074 of thedetection system 1700.

After the centrifuging process, the rotor 2020 is rotated to an analysisposition (see FIGS. 22B and 23C) wherein the sample element 2448 ispositioned within the slot 2074. With the rotor 2020 and sample element2448 in the analysis position, the analyte detection system 1700 cananalyze one or more of the components of the sample carried in thesample element 2448. For example, the detection system 1700 can analyzeat least one of the components that is separated out during thecentrifuging process. After using the cassette 820, the cassette 820 canbe removed from the main instrument 810 and discarded. Another cassette820 can then be mounted to the main instrument 810.

With reference to FIG. 23A, the illustrated cassette 820 includes thehousing 2400 that surrounds the rotor assembly 2016, and the rotor 2020is pivotally connected to the housing 2400 by the rotor assembly 2016.The rotor 2020 includes a rotor interface 2051 for driving engagementwith the drive system 2030 upon placement of the cassette 820 on themain instrument 810.

In some embodiments, the cassette 820 is a disposable fluid handlingcassette. The reusable main instrument 810 can be used with any numberof cassettes 820 as desired. Additionally or alternatively, the cassette820 can be a portable, handheld cassette for convenient transport. Inthese embodiments, the cassette 820 can be manually mounted to orremoved from the main instrument 810. In some embodiments, the cassette820 may be a non disposable cassette which can be permanently coupled tothe main instrument 810.

FIGS. 25A and 25B illustrate the centrifugal rotor 2020, which iscapable of carrying a sample, such as bodily fluid. Thus, theillustrated centrifugal rotor 2020 can be considered a fluid handlingelement that can prepare a sample for analysis, as well as hold thesample during a spectroscopic analysis. The rotor 2020 preferablycomprises an elongate body 2446, at least one sample element 2448, andat least one bypass element 2452. The sample element 2448 and bypasselement 2452 can be located at opposing ends of the rotor 2020. Thebypass element 2452 provides a bypass flow path that can be used toclean or flush fluid passageways of the fluid handling and analysisapparatus 140 without passing fluid through the sample element 2448.

The illustrated rotor body 2446 can be a generally planar member thatdefines a mounting aperture 2447 for coupling to the drive system 2030.The illustrated rotor 2020 has a somewhat rectangular shape. Inalternative embodiments, the rotor 2020 is generally circular,polygonal, elliptical, or can have any other shape as desired. Theillustrated shape can facilitate loading when positioned horizontally toaccommodate the analyte detection system 1700.

With reference to FIG. 25B, a pair of opposing first and second fluidconnectors 2027, 2029 extends outwardly from a front face of the rotor2020, to facilitate fluid flow through the rotor body 2446 to the sampleelement 2448 and bypass element 2452, respectively. The first fluidconnector 2027 defines an outlet port 2472 and an inlet port 2474 thatare in fluid communication with the sample element 2448. In theillustrated embodiment, fluid channels 2510, 2512 extend from the outletport 2472 and inlet port 2474, respectively, to the sample element 2448.(See FIGS. 25E and 25F.) As such, the ports 2472, 2474 and channels2510, 2512 define input and return flow paths through the rotor 2020 tothe sample element 2448 and back.

With continued reference to FIG. 25B, the rotor 2020 includes the bypasselement 2452 which permits fluid flow therethrough from an outlet port2572 to the inlet port 2574. A channel 2570 extends between the outletport 2572 and the inlet port 2574 to facilitate this fluid flow. Thechannel 2570 thus defines a closed flow path through the rotor 2020 fromone port 2572 to the other port 2574. In the illustrated embodiment, theoutlet port 2572 and inlet port 2574 of the bypass element 2452 havegenerally the same spacing therebetween on the rotor 2020 as the outletport 2472 and the inlet port 2474.

One or more windows 2460 a, 2460 b can be provided for optical accessthrough the rotor 2020. A window 2460 a proximate the bypass element2452 can be a through-hole (see FIG. 25E) that permits the passage ofelectromagnetic radiation through the rotor 2020. A window 2460 bproximate the sample element 2448 can also be a similar through-holewhich permits the passage of electromagnetic radiation. Alternatively,one or both of the windows 2460 a, 2460 b can be a sheet constructed ofcalcium fluoride, barium fluoride, germanium, silicon, polypropylene,polyethylene, combinations thereof, or any material with suitabletransmissivity (i.e., transmittance per unit thickness) in the relevantwavelength(s). The windows 2460 a, 2460 b are positioned so that one ofthe windows 2460 a, 2460 b is positioned in the slot 2074 when the rotor2020 is in a vertically orientated position.

Various fabrication techniques can be used to form the rotor 2020. Insome embodiments, the rotor 2020 can be formed by molding (e.g.,compression or injection molding), machining, or a similar productionprocess or combination of production processes. In some embodiments, therotor 2020 is comprised of plastic. The compliance of the plasticmaterial can be selected to create the seal with the ends of pins 2542,2544 of a fluid interface 2028 (discussed in further detail below).Non-limiting exemplary plastics for forming the ports (e.g., ports 2572,2574, 2472, 2474 ) can be relatively chemically inert and can beinjection molded or machined. These plastics include, but are notlimited to, PEEK and polyphenylenesulfide (PPS). Although both of theseplastics have high modulus, a fluidic seal can be made if sealingsurfaces are produced with smooth finish and the sealing zone is a smallarea where high contact pressure is created in a very small zone.Accordingly, the materials used to form the rotor 2020 and pins 2542,2544 can be selected to achieve the desired interaction between therotor 2020 and the pins 2542, 2544, as described in detail below.

The illustrated rotor assembly 2016 of FIG. 23A rotatably connects therotor 2020 to the cassette housing 2400 via a rotor axle boss 2426 whichis fixed with respect to the cassette housing and pivotally holds arotor axle 2430 and the rotor 2020 attached thereto. The rotor axle 2430extends outwardly from the rotor axle boss 2426 and is fixedly attachedto a rotor bracket 2436, which is preferably securely coupled to a rearface of the rotor 2020. Accordingly, the rotor assembly 2016 and thedrive system 2030 cooperate to ensure that the rotor 2020 rotates aboutthe axis 2024, even at high speeds. The illustrated cassette 820 has asingle rotor assembly 2016. In other embodiments, the cassette 820 canhave more than one rotor assembly 2016. Multiple rotor assemblies 2016can be used to prepare (preferably simultaneously) and test multiplesamples.

With reference again to FIGS. 25A, 25B, 25E and 25F, the sample element2448 is coupled to the rotor 2020 and can hold a sample of body fluidfor processing with the centrifuge. The sample element 2448 can, incertain embodiments, be generally similar to other sample elements orcuvettes disclosed herein (e.g., sample elements 1730, 2112) except asfurther detailed below.

The sample element 2448 comprises a sample chamber 2464 that holds asample for centrifuging, and fluid channels 2466, 2468, which providefluid communication between the chamber 2464 and the channels 2512,2510, respectively, of the rotor 2020. Thus, the fluid channels 2512,2466 define a first flow path between the port 2474 and the chamber2464, and the channels 2510, 2468 define a second flow path between theport 2472 and the chamber 2464. Depending on the direction of fluid flowinto the sample element 2448, either of the first or second flow pathscan serve as an input flow path, and the other can serve as a returnflow path.

A portion of the sample chamber 2464 can be considered an interrogationregion 2091, which is the portion of the sample chamber through whichelectromagnetic radiation passes during analysis by the detection system1700 of fluid contained in the chamber 2464. Accordingly, theinterrogation region 2091 is aligned with the window 2460 b when thesample element 2448 is coupled to the rotor 2020. The illustratedinterrogation region 2091 comprises a radially inward portion (i.e.,relatively close to the axis of rotation 2024 of the rotor 2020) of thechamber 2464, to facilitate spectroscopic analysis of the lower densityportion(s) of the body fluid sample (e.g., the plasma of a whole bloodsample) after centrifuging, as will be discussed in greater detailbelow. Where the higher-density portions of the body fluid sample are ofinterest for spectroscopic analysis, the interrogation region 2091 canbe located in a radially outward (i.e., further from the axis ofrotation 2024 of the rotor 2020) portion of the chamber 2464.

The rotor 2020 can temporarily or permanently hold the sample element2448. As shown in FIG. 25F, the rotor 2020 forms a recess 2502 whichreceives the sample element 2448. The sample element 2448 can be held inthe recess 2502 by frictional interaction, adhesives, or any othersuitable coupling means. The illustrated sample element 2448 is recessedin the rotor 2020. However, the sample element 2448 can alternativelyoverlie or protrude from the rotor 2020.

The sample element 2448 can be used for a predetermined length of time,to prepare a predetermined amount of sample fluid, to perform a numberof analyses, etc. If desired, the sample element 2448 can be removedfrom the rotor 2020 and then discarded. Another sample element 2448 canthen be placed into the recess 2502. Thus, even if the cassette 820 isdisposable, a plurality of disposable sample elements 2448 can be usedwith a single cassette 820. Accordingly, a single cassette 820 can beused with any number of sample elements as desired. Alternatively, thecassette 820 can have a sample element 2448 that is permanently coupledto the rotor 2020. In some embodiments, at least a portion of the sampleelement 2448 is integrally or monolithically formed with the rotor body2446. Additionally or alternatively, the rotor 2020 can comprise aplurality of sample elements (e.g., with a record sample element inplace of the bypass 2452 ). In this embodiment, a plurality of samples(e.g., bodily fluid) can be prepared simultaneously to reduce samplepreparation time.

FIGS. 26A and 26B illustrate a layered construction technique which canbe employed when forming certain embodiments of the sample element 2448.The depicted layered sample element 2448 comprises a first layer 2473, asecond layer 2475, and a third layer 2478. The second layer 2475 ispreferably positioned between the first layer 2473 and the third layer2478. The first layer 2473 forms an upper chamber wall 2482, and thethird layer 2478 forms a lower chamber wall 2484. A lateral wall 2490 ofthe second layer 2475 defines the sides of the chamber 2464 and thefluid channels 2466, 2468.

The second layer 2475 can be formed by die-cutting a substantiallyuniform-thickness sheet of a material to form the lateral wall patternshown in FIG. 26A. The second layer 2475 can comprise a layer oflightweight flexible material, such as a polymer material, with adhesivedisposed on either side thereof to adhere the first and third layers2473, 2478 to the second layer 2475 in “sandwich” fashion as shown inFIG. 26B. Alternatively, the second layer 2475 can comprise an“adhesive-only” layer formed from a uniform-thickness sheet of adhesivewhich has been die-cut to form the depicted lateral wall pattern.

However constructed, the second layer 2475 is preferably of uniformthickness to define a substantially uniform thickness or path length ofthe sample chamber 2464 and/or interrogation region 2091. This pathlength (and therefore the thickness of the second layer 2475 as well) ispreferably between 10 microns and 100 microns, or is 20, 40, 50, 60, or80 microns, in various embodiments.

The upper chamber wall 2482, lower chamber wall 2484, and lateral wall2490 cooperate to form the chamber 2464. The upper chamber wall 2482and/or the lower chamber wall 2484 can permit the passage ofelectromagnetic energy therethrough. Accordingly, one or both of thefirst and third layers 2473, 2478 comprises a sheet or layer of materialwhich is relatively or highly transmissive of electromagnetic radiation(preferably infrared radiation or mid-infrared radiation) such as bariumfluoride, silicon, polyethylene or polypropylene. If only one of thelayers 2473, 2478 is so transmissive, the other of the layers ispreferably reflective, to back-reflect the incoming radiation beam fordetection on the same side of the sample element 2448 as it was emitted.Thus the upper chamber wall 2482 and/or lower chamber wall 2484 can beconsidered optical window(s). These window(s) are disposed on one orboth sides of the interrogation region 2091 of the sample element 2448.

In one embodiment, sample element 2448 has opposing sides that aretransmissive of infrared radiation and suitable for making opticalmeasurements as described, for example, in U.S. Patent ApplicationPublication No. 2005/0036146, published Feb. 17, 2005, titled SAMPLEELEMENT QUALIFICATION, and hereby incorporated by reference and made apart of this specification. Except as further described herein, theembodiments, features, systems, devices, materials, methods andtechniques described herein may, in some embodiments, be similar to anyone or more of the embodiments, features, systems, devices, materials,methods and techniques described in U.S. Patent Application PublicationNo. 2003/0090649, published on May 15, 2003, titled REAGENT-LESSWHOLE-BLOOD GLUCOSE METER; or in U.S. Patent Application Publication No.2003/0086075, published on May 8, 2003, titled DEVICE AND METHOD FOR INVITRO DETERMINATION OF ANALYTE CONCENTRATIONS WITHIN BODY FLUIDS; or inU.S. Patent Application Publication No. 2004/0019431, published on Jan.29, 2004, titled METHOD OF DETERMINING AN ANALYTE CONCENTRATION IN ASAMPLE FROM AN ABSORPTION SPECTRUM, or in U.S. Pat. No. 6,652,136,issued on Nov. 25, 2003 to Marziali, titled METHOD OF SIMULTANEOUSMIXING OF SAMPLES. In addition, the embodiments, features, systems,devices, materials, methods and techniques described herein may, incertain embodiments, be applied to or used in connection with any one ormore of the embodiments, features, systems, devices, materials, methodsand techniques disclosed in the above-mentioned U.S. Patent ApplicationsPublications Nos. 2003/0090649; 2003/0086075; 2004/0019431; or U.S. Pat.No. 6,652,136. All of the above-mentioned publications and patent arehereby incorporated by reference herein and made a part of thisspecification.

With reference to FIGS. 23B and 23C, the cassette 820 can furthercomprise the movable fluid interface 2028 for filling and/or removingsample liquid from the sample element 2448. In the depicted embodiment,the fluid interface 2028 is rotatably mounted to the housing 2400 of thecassette 820. The fluid interface 2028 can be actuated between a loweredposition (FIG. 22C) and a raised or filling position (FIG. 27C). Whenthe interface 2028 is in the lowered position, the rotor 2020 can freelyrotate. To transfer sample fluid to the sample element 2448, the rotor2020 can be held stationary and in a sample element loading position(see FIG. 22C) the fluid interface 2028 can be actuated, as indicated bythe arrow 2590, upwardly to the filling position. When the fluidinterface 2028 is in the filling position, the fluid interface 2028 candeliver sample fluid into the sample element 2448 and/or remove samplefluid from the sample element 2448.

With continued reference to FIGS. 27A and 27B, the fluid interface 2028has a main body 2580 that is rotatably mounted to the housing 2400 ofthe cassette 820. Opposing brackets 2581, 2584 can be employed torotatably couple the main body 2580 to the housing 2400 of the cassette820, and permit rotation of the main body 2580 and the pins 2542, 2544about an axis of rotation 2590 between the lowered position and thefilling position. The main instrument 810 can include a horizontallymoveable actuator (not shown) in the form of a solenoid, pneumaticactuator, etc. which is extendible through an opening 2404 in thecassette housing 2400 (see FIG. 23B). Upon extension, the actuatorstrikes the main body 2580 of the fluid interface 2028, causing the body2580 to rotate to the filling position shown in FIG. 27C. The main body2580 is preferably spring-biased towards the retracted position (shownin FIG. 23A) so that retraction of the actuator allows the main body toreturn to the retracted position. The fluid interface 2028 can thus beactuated for periodically placing fluid passageways of the pins 2542,2544 in fluid communication with a sample element 2448 located on therotor 2020.

The fluid interface 2028 of FIGS. 27A and 23B includes fluid connectors2530, 2532 that can provide fluid communication between the interface2028 and one or more of the fluid passageways of the apparatus 140and/or sampling system 100/800, as will be discussed in further detailbelow. The illustrated connectors 2530, 2532 are in an upwardlyextending orientation and positioned at opposing ends of the main body2580. The connectors 2530, 2532 can be situated in other orientationsand/or positioned at other locations along the main body 2580. The mainbody 2580 includes a first inner passageway (not shown) which providesfluid communication between the connector 2530 and the pin 2542, and asecond inner passageway (not shown) which provides fluid communicationbetween the connector 2532 and the pin 2544.

The fluid pins 2542, 2544 extend outwardly from the main body 2580 andcan engage the rotor 2020 to deliver and/or remove sample fluid to orfrom the rotor 2020. The fluid pins 2542, 2544 have respective pinbodies 2561, 2563 and pin ends 2571, 2573. The pin ends 2571, 2573 aresized to fit within corresponding ports 2472, 2474 of the fluidconnector 2027 and/or the ports 2572, 2574 of the fluid connector 2029,of the rotor 2020. The pin ends 2571, 2573 can be slightly chamfered attheir tips to enhance the sealing between the pin ends 2571, 2573 androtor ports. In some embodiments, the outer diameters of the pin ends2573, 2571 are slightly larger than the inner diameters of the ports ofthe rotor 2020 to ensure a tight seal, and the inner diameters of thepins 2542, 2544 are preferably identical or very close to the innerdiameters of the channels 2510, 2512 leading from the ports. In otherembodiments, the outer diameter of the pin ends 2571, 2573 are equal toor less than the inner diameters of the ports of the rotor 2020.

The connections between the pins 2542, 2544 and the correspondingportions of the rotor 2020, either the ports 2472, 2474 leading to thesample element 2448 or the ports 2572, 2574 leading to the bypasselement 2452, can be relatively simple and inexpensive. At least aportion of the rotor 2020 can be somewhat compliant to help ensure aseal is formed with the pins 2542, 2544. Alternatively or additionally,sealing members (e.g., gaskets, O-rings, and the like) can be used toinhibit leaking between the pin ends 2571, 2573 and corresponding ports2472, 2474, 2572, 2574.

FIGS. 23A and 23B illustrate the cassette housing 2400 enclosing therotor assembly 2016 and the fluid interface 2028. The housing 2400 canbe a modular body that defines an aperture or opening 2404 dimensionedto receive a drive system housing 2050 when the cassette 820 isoperatively coupled to the main instrument 810. The housing 2400 canprotect the rotor 2020 from external forces and can also limitcontamination of samples delivered to a sample element in the rotor2020, when the cassette 820 is mounted to the main instrument 810.

The illustrated cassette 820 has a pair of opposing side walls 2041,2043, top 2053, and a notch 2408 for mating with the detection system1700. A front wall 2045 and rear wall 2047 extend between the side walls2041, 2043. The rotor assembly 2016 is mounted to the inner surface ofthe rear wall 2047. The front wall 2045 is configured to mate with themain instrument 810 while providing the drive system 2030 with access tothe rotor assembly 2016.

The illustrated front wall 2045 has the opening 2404 that providesaccess to the rotor assembly 2016. The drive system 2030 can be passedthrough the opening 2404 into the interior of the cassette 820 until itoperatively engages the rotor assembly 2016. The opening 2404 of FIG.23B is configured to mate and tightly surround the drive system 2030.The illustrated opening 2404 is generally circular and includes an uppernotch 2405 to permit the fluid interface actuator of the main instrument810 to access the fluid interface 2028, as discussed above. The opening2404 can have other configurations suitable for admitting the drivesystem 2030 and actuator into the cassette 820.

The notch 2408 of the housing 2400 can at least partially surround theprojecting portion of the analyte detection system 1700 when thecassette 820 is loaded onto the main instrument 810. The illustratednotch 2408 defines a cassette slot 2410 (FIG. 23A) that is aligned withelongate slot 2074 shown in FIG. 22C, upon loading of the cassette 820.The rotating rotor 2020 can thus pass through the aligned slots 2410,2074. In some embodiments, the notch 2408 has a generally U-shaped axialcross section as shown. More generally, the configuration of the notch2408 can be selected based on the design of the projecting portion ofthe detection system 1700.

Although not illustrated, fasteners, clips, mechanical fasteningassemblies, snaps, or other coupling means can be used to ensure thatthe cassette 820 remains coupled to the main instrument 810 duringoperation. Alternatively, the interaction between the housing 2400 andthe components of the main instrument 810 can secure the cassette 820 tothe main instrument 810.

FIG. 28 is a cross-sectional view of the main instrument 810. Theillustrated centrifuge drive system 2030 extends outwardly from a frontface 2046 of the main instrument 810 so that it can be easily mated withthe rotor assembly 2016 of the cassette 820. When the centrifuge drivesystem 2030 is energized, the drive system 2030 can rotate the rotor2020 at a desired rotational speed.

The illustrated centrifuge drive system 2030 of FIGS. 23E and 28includes a centrifuge drive motor 2038 and a drive spindle 2034 that isdrivingly connected to the drive motor 2038. The drive spindle 2034extends outwardly from the drive motor 2038 and forms a centrifugeinterface 2042. The centrifuge interface 2042 extends outwardly from thedrive system housing 2050, which houses the drive motor 2038. To impartrotary motion to the rotor 2020, the centrifuge interface 2042 can havekeying members, protrusions, notches, detents, recesses, pins, or othertypes of structures that can engage the rotor 2020 such that the drivespindle 2034 and rotor 2020 are coupled together.

The centrifuge drive motor 2038 of FIG. 28 can be any suitable motorthat can impart rotary motion to the rotor 2020. When the drive motor2038 is energized, the drive motor 2038 can rotate the drive spindle2034 at constant or varying speeds. Various types of motors, including,but not limited to, centrifuge motors, stepper motors, spindle motors,electric motors, or any other type of motor for outputting a torque canbe utilized. The centrifuge drive motor 2038 is preferably fixedlysecured to the drive system housing 2050 of the main instrument 810.

The drive motor 2038 can be the type of motor typically used in personalcomputer hard drives that is capable of rotating at about 7,200 RPM onprecision bearings, such as a motor of a Seagate Model ST380011A harddrive (Seagate Technology, Scotts Valley, Calif.) or similar motor. Inone embodiment, the drive spindle 2034 may be rotated at 6,000 rpm,which yields approximately 2,000 G's for a rotor having a 2.5 inch (64millimeter) radius. In another embodiment, the drive spindle 2034 may berotated at speeds of approximately 7,200 rpm. The rotational speed ofthe drive spindle 2034 can be selected to achieve the desiredcentrifugal force applied to a sample carried by the rotor 2020.

The main instrument 810 includes a main housing 2049 that defines achamber sized to accommodate a filter wheel assembly 2300 including afilter drive motor 2320 and filter wheel 2310 of the analyte detectionsystem 1700. The main housing 2049 defines a detection system opening3001 configured to receive an analyte detection system housing 2070. Theillustrated analyte detection system housing 2070 extends or projectsoutwardly from the housing 2049.

The main instrument 810 of FIGS. 23C and 23E includes a bubble sensorunit 321, a pump 2619 in the form of a peristaltic pump roller 2620 aand a roller support 2620 b, and valves 323 a, 323 b. The illustratedvalves 323 a, 323 b are pincher pairs, although other types of valvescan be used. When the cassette 820 is installed, these components canengage components of a fluid handling network 2600 of the cassette 820,as will be discussed in greater detail below.

With continued reference to FIG. 28, the analyte detection systemhousing 2070 surrounds and houses some of the internal components of theanalyte detection system 1700. The elongate slot 2074 extends downwardlyfrom an upper face 2072 of the housing 2070. The elongated slot 2074 issized and dimensioned so as to receive a portion of the rotor 2020. Whenthe rotor 2020 rotates, the rotor 2020 passes periodically through theelongated slot 2074. When a sample element of the rotor 2020 is in thedetection region 2080 defined by the slot 2074, the analyte detectionsystem 1700 can analyze material in the sample element.

The analyte detection system 1700 can be a spectroscopic bodily fluidanalyzer that preferably comprises an energy source 1720. The energysource 1720 can generate an energy beam directed along a major opticalaxis X that passes through the slot 2074 towards a sample detector 1745.The slot 2074 thus permits at least a portion of the rotor (e.g., theinterrogation region 2091 or sample chamber 2464 of the sample element2448) to be positioned on the optical axis X. To analyze a samplecarried by the sample element 2448, the sample element and sample can bepositioned in the detection region 2080 on the optical axis X such thatlight emitted from the source 1720 passes through the slot 2074 and thesample disposed within the sample element 2448.

The analyte detection system 1700 can also comprise one or more lensespositioned to transmit energy outputted from the energy source 1720. Theillustrated analyte detection system 1700 of FIG. 28 comprises a firstlens 2084 and a second lens 2086. The first lens 2084 is configured tofocus the energy from the source 1720 generally onto the sample elementand material sample. The second lens 2086 is positioned between thesample element and the sample detector 1745. Energy from energy source1720 passing through the sample element can subsequently pass throughthe second lens 2086. A third lens 2090 is preferably positioned betweena beam splitter 2093 and a reference detector 2094. The referencedetector 2094 is positioned to receive energy from the beam splitter2093.

The analyte detection system 1700 can be used to determine the analyteconcentration in the sample carried by the rotor 2020. Other types ofdetection or analysis systems can be used with the illustratedcentrifuge apparatus or sample preparation unit. The fluid handling andanalysis apparatus 140 is shown for illustrative purposes as being usedin conjunction with the analyte detection system 1700, but neither thesample preparation unit nor analyte detection system are intended to belimited to the illustrated configuration, or to be limited to being usedtogether.

To assemble the fluid handling and analysis apparatus 140, the cassette820 can be moved towards and installed onto the main instrument 810, asindicated by the arrow 2007 in FIG. 22A. As the cassette 820 isinstalled, the drive system 2030 passes through the aperture 2040 sothat the spindle 2034 mates with the rotor 2020. Simultaneously, theprojecting portion of the detection system 1700 is received in the notch2408 of the cassette 820. When the cassette 820 is installed on the maininstrument 810, the slot 2410 of the notch 2048 and the slot 2074 of thedetection system 1700 are aligned as shown in FIG. 22C. Accordingly,when the cassette 820 and main instrument 810 are assembled, the rotor2020 can rotate about the axis 2024 and pass through the slots 2410,2074.

After the cassette 820 is assembled with the main instrument 810, asample can be added to the sample element 2448. The cassette 820 can beconnected to an infusion source and a patient to place the system influid communication with a bodily fluid to be analyzed. Once thecassette 820 is connected to a patient, a bodily fluid may be drawn fromthe patient into the cassette 820. The rotor 2020 is rotated to avertical loading position wherein the sample element 2448 is near thefluid interface 2028 and the bypass element 2452 is positioned withinthe slot 2074 of the detection system 1700. Once the rotor 2020 is inthe vertical loading position, the pins 2542, 2544 of the fluidinterface 2028 are positioned to mate with the ports 2472, 2474 of therotor 2020. The fluid interface 2028 is then rotated upwardly until theends 2571, 2573 of the pins 2542, 2544 are inserted into the ports 2472,2474.

When the fluid interface 2028 and the sample element 2448 are thusengaged, sample fluid (e.g., whole blood) is pumped into the sampleelement 2448. The sample can flow through the pin 2544 into and throughthe rotor channel 2512 and the sample element channel 2466, and into thesample chamber 2464. As shown in FIG. 25C, the sample chamber 2464 canbe partially or completely filled with sample fluid. In someembodiments, the sample fills at least the sample chamber 2464 and theinterrogation region 2091 of the sample element 2448. The sample canoptionally fill at least a portion of the sample element channels 2466,2468. The illustrated sample chamber 2464 is filled with whole blood,although the sample chamber 2464 can be filled with other substances.After the sample element 2448 is filled with a desired amount of fluid,the fluid interface 2028 can be moved to a lowered position to permitrotation of the rotor 2020.

The centrifuge drive system 2030 can then spin the rotor 2020 andassociated sample element 2448 as needed to separate one or morecomponents of the sample. The separated component(s) of the sample maycollect or be segregated in a section of the sample element foranalysis. In the illustrated embodiment, the sample element 2448 of FIG.25C is filled with whole blood prior to centrifuging. The centrifugalforces can be applied to the whole blood until plasma 2594 is separatedfrom the blood cells 2592. After centrifuging, the plasma 2594 ispreferably located in a radially inward portion of the sample element2448, including the interrogation region 2091. The blood cells 2592collect in a portion of the sample chamber 2464 which is radiallyoutward of the plasma 2594 and interrogation region 2091.

The rotor 2020 can then be moved to a vertical analysis position whereinthe sample element 2448 is disposed within the slot 2074 and alignedwith the source 1720 and the sample detector 1745 on the major opticalaxis X. When the rotor 2020 is in the analysis position, theinterrogation portion 2091 is preferably aligned with the major opticalaxis X of the detection system 1700. The analyte detection system 1700can analyze the sample in the sample element 2448 using spectroscopicanalysis techniques as discussed elsewhere herein.

After the sample has been analyzed, the sample can be removed from thesample element 2448. The sample may be transported to a waste receptacleso that the sample element 2448 can be reused for successive sampledraws and analyses. The rotor 2020 is rotated from the analysis positionback to the vertical loading position. To empty the sample element 2448,the fluid interface 2028 can again engage the sample element 2448 toflush the sample element 2448 with fresh fluid (either a new sample ofbody fluid, or infusion fluid). The fluid interface 2028 can be rotatedto mate the pins 2542, 2544 with the ports 2472, 2474 of the rotor 2020.The fluid interface 2028 can pump a fluid through one of the pins 2542,2544 until the sample is flushed from the sample element 2448. Varioustypes of fluids, such as infusion liquid, air, water, and the like, canbe used to flush the sample element 2448. After the sample element 2448has been flushed, the sample element 2448 can once again be filled withanother sample.

In an alternative embodiment, the sample element 2448 may be removedfrom the rotor 2020 and replaced after each separate analysis, or aftera certain number of analyses. Once the patient care has terminated, thefluid passageways or conduits may be disconnected from the patient andthe sample cassette 820 which has come into fluid contact with thepatient's bodily fluid may be disposed of or sterilized for reuse. Themain instrument 810, however, has not come into contact with thepatient's bodily fluid at any point during the analysis and thereforecan readily be connected to a new fluid handling cassette 820 and usedfor the analysis of a subsequent patient.

The rotor 2020 can be used to provide a fluid flow bypass. To facilitatea bypass flow, the rotor 2020 is first rotated to the verticalanalysis/bypass position wherein the bypass element 2452 is near thefluid interface 2028 and the sample element 2448 is in the slot 2074 ofthe analyte detection system 1700. Once the rotor 2020 is in thevertical analysis/bypass position, the pins 2542, 2544 can mate with theports 2572, 2574 of the rotor 2020. In the illustrated embodiment, thefluid interface 2028 is rotated upwardly until the ends 2571, 2573 ofthe pins 2542, 2544 are inserted into the ports 2572, 2574. The bypasselement 2452 can then provide a completed fluid circuit so that fluidcan flow through one of the pins 2542, 2544 into the bypass element2452, through the bypass element 2452, and then through the other pin2542, 2544. The bypass element 2452 can be utilized in this manner tofacilitate the flushing or sterilizing of a fluid system connected tothe cassette 820.

As shown in FIG. 23B, the cassette 820 preferably includes the fluidhandling network 2600 which can be employed to deliver fluid to thesample element 2448 in the rotor 2020 for analysis. The main instrument810 has a number of components that can, upon installation of thecassette 820 on the main instrument 810, extend through openings in thefront face 2045 of cassette 820 to engage and interact with componentsof the fluid handling network 2600, as detailed below.

The fluid handling network 2600 of the fluid handling and analysisapparatus 140 includes the passageway 111 which extends from theconnector 120 toward and through the cassette 820 until it becomes thepassageway 112, which extends from the cassette 820 to the patientconnector 110. A portion 111 a of the passageway 111 extends across anopening 2613 in the front face 2045 of the cassette 820. When thecassette 820 is installed on the main instrument 810, the roller pump2619 engages the portion 111 a, which becomes situated between theimpeller 2620 a and the impeller support 2620 b (see FIG. 23C).

The fluid handling network 2600 also includes passageway 113 whichextends from the patient connector 110 towards and into the cassette820. After entering the cassette 820, the passageway 113 extends acrossan opening 2615 in the front face 2045 to allow engagement of thepassageway 113 with a bubble sensor 321 of the main instrument 810, whenthe cassette 820 is installed on the main instrument 810. The passageway113 then proceeds to the connector 2532 of the fluid interface 2028,which extends the passageway 113 to the pin 2544. Fluid drawn from thepatient into the passageway 113 can thus flow into and through the fluidinterface 2028, to the pin 2544. The drawn body fluid can further flowfrom the pin 2544 and into the sample element 2448, as detailed above.

A passageway 2609 extends from the connector 2530 of the fluid interface2028 and is thus in fluid communication with the pin 2542. Thepassageway 2609 branches to form the waste line 324 and the pump line327. The waste line 324 passes across an opening 2617 in the front face2045 and extends to the waste receptacle 325. The pump line 327 passesacross an opening 2619 in the front face 2045 and extends to the pump328. When the cassette 820 is installed on the main instrument 810, thepinch valves 323 a, 323 b extend through the openings 2617, 2619 toengage the lines 324, 327, respectively.

The waste receptacle 325 is mounted to the front face 2045. Waste fluidpassing from the fluid interface 2028 can flow through the passageways2609, 324 and into the waste receptacle 325. Once the waste receptacle325 is filled, the cassette 820 can be removed from the main instrument810 and discarded. Alternatively, the filled waste receptacle 325 can bereplaced with an empty waste receptacle 325.

The pump 328 can be a displacement pump (e.g., a syringe pump). A pistoncontrol 2645 can extend over at least a portion of an opening 2621 inthe cassette face 2045 to allow engagement with an actuator 2652 whenthe cassette 820 is installed on the main instrument 810. When thecassette 820 is installed, the actuator 2652 (FIG. 23E) of the maininstrument 810 engages the piston control 2645 of the pump 328 and candisplace the piston control 2645 for a desired fluid flow.

It will be appreciated that, upon installing the cassette 820 of FIG.23A on the main instrument 810 of FIG. 23E, there is formed (as shown inFIG. 23E) a fluid circuit similar to that shown in the sampling unit 200in FIG. 3. This fluid circuit can be operated in a manner similar tothat described above in connection with the apparatus of FIG. 3 (e.g.,in accordance with the methodology illustrated in FIGS. 7A-7J and Table1).

FIG. 24A depicts another embodiment of a fluid handling network 2700that can be employed in the cassette 820. The fluid handling network2700 can be generally similar in structure and function to the network2600 of FIG. 23B, except as detailed below. The network 2700 includesthe passageway 111 which extends from the connector 120 toward andthrough the cassette 820 until it becomes the passageway 112, whichextends from the cassette 820 to the patient connector 110. A portion111 a of the passageway 111 extends across an opening 2713 in the frontface 2745 of the cassette 820. When the cassette 820 is installed on themain instrument 810, a roller pump 2619 of the main instrument 810 ofFIG. 24B can engage the portion 111 a in a manner similar to thatdescribed above with respect to FIGS. 23B-23C. The passageway 113extends from the patient connector 110 towards and into the cassette820. After entering the cassette 820, the passageway 113 extends acrossan opening 2763 in the front face 2745 to allow engagement with a valve2733 of the main instrument 810. A waste line 2704 extends from thepassageway 113 to the waste receptacle 325 and across an opening 2741 inthe front face 2745. The passageway 113 proceeds to the connector 2532of the fluid interface 2028, which extends the passageway 113 to the pin2544. The passageway 113 crosses an opening 2743 in the front face 2745to allow engagement of the passageway 113 with a bubble sensor 2741 ofthe main instrument 810 of FIG. 24B. When the cassette 820 is installedon the main instrument 810, the pinch valves 2732, 2733 extend throughthe openings 2731, 2743 to engage the passageways 113, 2704,respectively.

The illustrated fluid handling network 2700 also includes a passageway2723 which extends between the passageway 111 and a passageway 2727,which in turn extends between the passageway 2723 and the fluidinterface 2028. The passageway 2727 extends across an opening 2733 inthe front face 2745. A pump line 2139 extends from a pump 328 to thepassageways 2723, 2727. When the cassette 820 is installed on the maininstrument 810, the pinch valves 2716, 2718 extend through the openings2725, 2733 in the front face 2745 to engage the passageways 2723, 2727,respectively.

It will be appreciated that, upon installing the cassette 820 on themain instrument 810 (as shown in FIG. 24A), there is formed a fluidcircuit that can be operated in a manner similar to that describedabove, in connection with the apparatus of FIGS. 9-10.

In view of the foregoing, it will be further appreciated that thevarious embodiments of the fluid handling and analysis apparatus 140(comprising a main instrument 810 and cassette 820) depicted in FIGS.22A-28 can serve as the fluid handling and analysis apparatus 140 of anyof the sampling systems 100/300/500, or the fluid handling system 10,depicted in FIGS. 1-5 herein. In addition, the fluid handling andanalysis apparatus 140 of FIGS. 22A-28 can, in certain embodiments, besimilar to the apparatus 140 of FIGS. 1-2 or 8-10, except as furtherdescribed above.

Section V—Methods for Determining Analyte Concentrations from SampleSpectra

This section discusses a number of computational methods or algorithmswhich may be used to calculate the concentration of the analyte(s) ofinterest in the sample S, and/or to compute other measures that may beused in support of calculations of analyte concentrations. Any one orcombination of the algorithms disclosed in this section may reside asprogram instructions stored in the memory 212 so as to be accessible forexecution by the processor 210 of the fluid handling and analysisapparatus 140 or analyte detection system 334 to compute theconcentration of the analyte(s) of interest in the sample, or otherrelevant measures.

Several disclosed embodiments are devices and methods for analyzingmaterial sample measurements and for quantifying one or more analytes inthe presence of interferents. Interferents can comprise components of amaterial sample being analyzed for an analyte, where the presence of theinterferent affects the quantification of the analyte. Thus, forexample, in the spectroscopic analysis of a sample to determine ananalyte concentration, an interferent could be a compound havingspectroscopic features that overlap with those of the analyte. Thepresence of such an interferent can introduce errors in thequantification of the analyte. More specifically, the presence ofinterferents can affect the sensitivity of a measurement technique tothe concentration of analytes of interest in a material sample,especially when the system is calibrated in the absence of, or with anunknown amount of, the interferent.

Independently of or in combination with the attributes of interferentsdescribed above, interferents can be classified as being endogenous(i.e., originating within the body) or exogenous (i.e., introduced fromor produced outside the body). As example of these classes ofinterferents, consider the analysis of a blood sample (or a bloodcomponent sample or a blood plasma sample) for the analyte glucose.Endogenous interferents include those blood components having originswithin the body that affect the quantification of glucose, and mayinclude water, hemoglobin, blood cells, and any other component thatnaturally occurs in blood. Exogenous interferents include those bloodcomponents having origins outside of the body that affect thequantification of glucose, and can include items administered to aperson, such as medicaments, drugs, foods or herbs, whether administeredorally, intravenously, topically, etc.

Independently of or in combination with the attributes of interferentsdescribed above, interferents can comprise components which are possiblybut not necessarily present in the sample type under analysis. In theexample of analyzing samples of blood or blood plasma drawn frompatients who are receiving medical treatment, a medicament such asacetaminophen is possibly, but not necessarily present in this sampletype. In contrast, water is necessarily present in such blood or plasmasamples.

To facilitate an understanding of the inventions, embodiments arediscussed herein where one or more analyte concentrations are obtainedusing spectroscopic measurements of a sample at wavelengths includingone or more wavelengths that are identified with the analyte(s). Theembodiments disclosed herein are not meant to limit, except as claimed,the scope of certain disclosed inventions which are directed to theanalysis of measurements in general.

As an example, certain disclosed methods are used to quantitativelyestimate the concentration of one specific compound (an analyte) in amixture from a measurement, where the mixture contains compounds(interferents) that affect the measurement. Certain disclosedembodiments are particularly effective if each analyte and interferentcomponent has a characteristic signature in the measurement, and if themeasurement is approximately affine (i.e., includes a linear componentand an offset) with respect to the concentration of each analyte andinterferent. In one embodiment, a method includes a calibration processincluding an algorithm for estimating a set of coefficients and anoffset value that permits the quantitative estimation of an analyte. Inanother embodiment, there is provided a method for modifying hybridlinear algorithm (HLA) methods to accommodate a random set ofinterferents, while retaining a high degree of sensitivity to thedesired component. The data employed to accommodate the random set ofinterferents are (a) the signatures of each of the members of the familyof potential additional components and (b) the typical quantitativelevel at which each additional component, if present, is likely toappear.

Certain methods disclosed herein are directed to the estimation ofanalyte concentrations in a material sample in the possible presence ofan interferent. In certain embodiments, any one or combination of themethods disclosed herein may be accessible and executable processor 210of system 334. Processor 210 may be connected to a computer network, anddata obtained from system 334 can be transmitted over the network to oneor more separate computers that implement the methods. The disclosedmethods can include the manipulation of data related to samplemeasurements and other information supplied to the methods (including,but not limited to, interferent spectra, sample population models, andthreshold values, as described subsequently). Any or all of thisinformation, as well as specific algorithms, may be updated or changedto improve the method or provide additional information, such asadditional analytes or interferents.

Certain disclosed methods generate a “calibration constant” that, whenmultiplied by a measurement, produces an estimate of an analyteconcentration. Both the calibration constant and measurement cancomprise arrays of numbers. The calibration constant is calculated tominimize or reduce the sensitivity of the calibration to the presence ofinterferents that are identified as possibly being present in thesample. Certain methods described herein generate a calibration constantby: 1) identifying the presence of possible interferents; and 2) usinginformation related to the identified interferents to generate thecalibration constant. These certain methods do not require that theinformation related to the interferents includes an estimate of theinterferent concentration—they merely require that the interferents beidentified as possibly present. In one embodiment, the method uses a setof training spectra each having known analyte concentration(s) andproduces a calibration that minimizes the variation in estimated analyteconcentration with interferent concentration. The resulting calibrationconstant is proportional to analyte concentration(s) and, on average, isnot responsive to interferent concentrations.

In one embodiment, it is not required (though not prohibited either)that the training spectra include any spectrum from the individual whoseanalyte concentration is to be determined. That is, the term “training”when used in reference to the disclosed methods does not requiretraining using measurements from the individual whose analyteconcentration will be estimated (e.g., by analyzing a bodily fluidsample drawn from the individual).

Several terms are used herein to describe the estimation process. Asused herein, the term “Sample Population” is a broad term and includes,without limitation, a large number of samples having measurements thatare used in the computation of a calibration—in other words, used totrain the method of generating a calibration. For an embodimentinvolving the spectroscopic determination of glucose concentration, theSample Population measurements can each include a spectrum (analysismeasurement) and a glucose concentration (analyte measurement). In oneembodiment, the Sample Population measurements are stored in a database,referred to herein as a “Population Database.”

The Sample Population may or may not be derived from measurements ofmaterial samples that contain interferents to the measurement of theanalyte(s) of interest. One distinction made herein between differentinterferents is based on whether the interferent is present in both theSample Population and the sample being measured, or only in the sample.As used herein, the term “Type-A interferent” refers to an interferentthat is present in both the Sample Population and in the material samplebeing measured to determine an analyte concentration. In certain methodsit is assumed that the Sample Population includes only interferents thatare endogenous, and does not include any exogenous interferents, andthus Type-A interferents are endogenous. The number of Type-Ainterferents depends on the measurement and analyte(s) of interest, andmay number, in general, from zero to a very large number. The materialsample being measured, for example sample S, may also includeinterferents that are not present in the Sample Population. As usedherein, the term “Type-B interferent” refers to an interferent that iseither: 1) not found in the Sample Population but that is found in thematerial sample being measured (e.g., an exogenous interferent), or 2)is found naturally in the Sample Population, but is at abnormally highconcentrations in the material sample (e.g., an endogenous interferent).Examples of a Type-B exogenous interferent may include medications, andexamples of Type-B endogenous interferents may include urea in personssuffering from renal failure. In the example of mid-IR spectroscopicabsorption measurement of glucose in blood, water is found in all bloodsamples, and is thus a Type-A interferent. For a Sample Population madeup of individuals who are not taking intravenous drugs, and a materialsample taken from a hospital patient who is being administered aselected intravenous drug, the selected drug is a Type-B interferent.

In one embodiment, a list of one or more possible Type-B Interferents isreferred to herein as forming a “Library of Interferents,” and eachinterferent in the library is referred to as a “Library Interferent.”The Library Interferents include exogenous interferents and endogenousinterferents that may be present in a material sample due, for example,to a medical condition causing abnormally high concentrations of theendogenous interferent.

In addition to components naturally found in the blood, the ingestion orinjection of some medicines or illicit drugs can result in very high andrapidly changing concentrations of exogenous interferents. This resultsin problems in measuring analytes in blood of hospital or emergency roompatients. An example of overlapping spectra of blood components andmedicines is illustrated in FIG. 29 as the absorption coefficient at thesame concentration and optical pathlength of pure glucose and threespectral interferents, specifically mannitol (chemical formula:hexane-1,2,3,4,5,6-hexaol), N acetyl L cysteine, dextran, andprocainamide (chemical formula:4-amino-N-(2-diethylaminoethyl)benzamid). FIG. 30 shows the logarithm ofthe change in absorption spectra from a Sample Population bloodcomposition as a function of wavelength for blood containing additionallikely concentrations of components, specifically, twice the glucoseconcentration of the Sample Population and various amounts of mannitol,N acetyl L cysteine, dextran, and procainamide. The presence of thesecomponents is seen to affect absorption over a wide range ofwavelengths. It can be appreciated that the determination of theconcentration of one species without a priori knowledge or independentmeasurement of the concentration of other species is problematic.

One method for estimating the concentration of an analyte in thepresence of interferents is presented in flowchart 3100 of FIG. 31 as afirst step (Block 3110) where a measurement of a sample is obtained, asecond step (Block 3120), where the obtained measurement data isanalyzed to identify possible interferents to the analyte, a third step(Block 3130) where a model is generated for predicting the analyteconcentration in the presence of the identified possible interferents,and a fourth step (Block 3140) where the model is used to estimate theanalyte concentration in the sample from the measurement. Preferably thestep of Block 3130 generates a model where the error is minimized forthe presence of the identified interferents that are not present in ageneral population of which the sample is a member.

The method Blocks 3110, 3120, 3130, and 3140 may be repeatedly performedfor each analyte whose concentration is required. Thus, for example,FIG. 49 shows a method 4900 which is substantially the same as themethod of Block 3100, except as noted in the following discussion. Ifone measurement is sensitive to two or more analytes, then the methodsof Blocks 3120, 3130, and 3140 may be repeated for each analyte, asindicated by an arrow 4903. If each analyte has a separate measurement,then the methods of Blocks 3110, 3120, 3130, and 3140 may be repeatedfor each analyze, as indicated by an arrow 4901.

The method Blocks 3110, 3120, 3130, and 3140 may be repeatedly performedfor each analyte whose concentration is required. If one measurement issensitive to two or more analytes, then the methods of Blocks 3120,3130, and 3140 may be repeated for each analyte. If each analyte has aseparate measurement, then the methods of Blocks 3110, 3120, 3130, and3140 may be repeated for each analyte.

An embodiment of the method of flowchart 3100 for the determination ofan analyte from spectroscopic measurements will now be discussed.Further, this embodiment will estimate the amount of glucoseconcentration in blood sample S, without limit to the scope of theinventions disclosed herein. In one embodiment, the measurement of Block3110 is an absorbance spectrum, C_(s)(λ_(i)), of a measurement sample Sthat has, in general, one analyte of interest, glucose, and one or moreinterferents. In one embodiment, the methods include generating acalibration constant κ(λ_(i)) that, when multiplied by the absorbancespectrum C_(s)(λ_(i)), provides an estimate, g_(est), of the glucoseconcentration g_(s).

As described subsequently, one embodiment of Block 3120 includes astatistical comparison of the absorbance spectrum of sample S with aspectrum of the Sample Population and combinations of individual LibraryInterferent spectra. After the analysis of Block 3120, a list of LibraryInterferents that are possibly contained in sample S has been identifiedand includes, depending on the outcome of the analysis of Block 3120,either no Library Interferents, or one or more Library Interferents.Block 3130 then generates a large number of spectra using the largenumber of spectra of the Sample Population and their respective knownanalyte concentrations and known spectra of the identified LibraryInterferents. Block 3130 then uses the generated spectra to generate acalibration constant matrix to convert a measured spectrum to an analyteconcentration that is the least sensitive to the presence of theidentified Library Interferents. Block 3140 then applies the generatedcalibration constant to predict the glucose concentration in sample S.

As indicated in Block 3110, a measurement of a sample is obtained. Forillustrative purposes, the measurement, C_(s)(λ_(i)), is assumed to be aplurality of measurements at different wavelengths, or analyzedmeasurements, on a sample indicating the intensity of light that isabsorbed by sample S. It is to be understood that spectroscopicmeasurements and computations may be performed in one or more domainsincluding, but not limited to, the transmittance, absorbance and/oroptical density domains. The measurement C_(s)(λ_(i)) is an absorption,transmittance, optical density or other spectroscopic measurement of thesample at selected wavelength or wavelength bands. Such measurements maybe obtained, for example, using analyte detection system 334. Ingeneral, sample S contains Type-A interferents, at concentrationspreferably within the range of those found in the Sample Population.

In one embodiment, absorbance measurements are converted to pathlengthnormalized measurements. Thus, for example, the absorbance is convertedto optical density by dividing the absorbance by the optical pathlength,L, of the measurement. In one embodiment, the pathlength L is measuredfrom one or more absorption measurements on known compounds. Thus, inone embodiment, one or more measurements of the absorption through asample S of water or saline solutions of known concentration are madeand the pathlength, L, is computed from the resulting absorptionmeasurement(s). In another embodiment, absorption measurements are alsoobtained at portions of the spectrum that are not appreciably affectedby the analytes and interferents, and the analyte measurement issupplemented with an absorption measurement at those wavelengths.

Some methods are “pathlength insensitive,” in that they can be used evenwhen the precise pathlength is not known beforehand. The sample can beplaced in the sample chamber 903 or 2464, sample element 1730 or 2448,or in a cuvette or other sample container. Electromagnetic radiation (inthe mid-infrared range, for example) can be emitted from a radiationsource so that the radiation travels through the sample chamber. Adetector can be positioned where the radiation emerges, on the otherside of the sample chamber from the radiation source, for example. Thedistance the radiation travels through the sample can be referred to asa “pathlength.” In some embodiments, the radiation detector can belocated on the same side of the sample chamber as the radiation source,and the radiation can reflect off one or more internal walls of thesample chamber before reaching the detector.

As discussed above, various substances can be inserted into the samplechamber. For example, a reference fluid such as water or saline solutioncan be inserted, in addition to a sample or samples containing ananalyte or analytes. In some embodiments, a saline reference fluid isinserted into the sample chamber and radiation is emitted through thatreference fluid. The detector measures the amount and/or characteristicsof the radiation that passes through the sample chamber and referencefluid without being absorbed or reflected. The measurement taken usingthe reference fluid can provide information relating to the pathlengthtraveled by the radiation. For example, data may already exist fromprevious measurements that have been taken under similar circumstances.That is, radiation can be emitted previously through sample chamberswith various known pathlengths to establish reference data that can bearranged in a “look-up table,” for example. With reference fluid in thesample chamber, a one-to-one correspondence can be experimentallyestablished between various detector readings and various pathlengths,respectively. This correspondence can be recorded in the look-up table,which can be recorded in a computer database or in electronic memory,for example.

One method of determining the radiation pathlength can be accomplishedwith a thin, empty sample chamber. In particular, this approach candetermine the thickness of a narrow sample chamber or cell with tworeflective walls. (Because the chamber will be filled with a sample,this same thickness corresponds to the “pathlength” radiation willtravel through the sample). A range of radiation wavelengths can beemitted in a continuous manner through the cell or sample chamber. Theradiation can enter the cell and reflect off the interior cell walls,bouncing back and forth between those walls one or multiple times beforeexiting the cell and passing into the radiation detector. This cancreate a periodic interference pattern or “fringe” with repeating maximaand minima. This periodic pattern can be plotted where the horizontalaxis is a range of wavelengths and the vertical axis is a range oftransmittance, measured as a percentage of total transmittance, forexample. The maxima occur when the radiation reflected off of the twointernal surfaces of the cell has traveled a distance that is anintegral multiple N of the wavelength of the radiation that wastransmitted without reflection. Constructive interference occurswhenever the wavelength is equal to 2b/N, where “b” is the thickness (orpathlength) of the cell. Thus, if ΔN is the number of maxima in thisfringe pattern for a given range of wavelengths λ₁-λ₂, then thethickness of the cell b is provided by the following relation:b=ΔN/2(λ₁-λ₂). This approach can be especially useful when therefractive index of the material within the sample chamber or fluid cellis not the same as the refractive index of the walls of the cell,because this condition improves reflection.

Once the pathlength has been determined, it can be used to calculate ordetermine a reference value or a reference spectrum for the interferents(such as protein or water) that may be present in a sample. For example,both an analyte such as glucose and an interferent such as water mayabsorb radiation at a given wavelength. When the source emits radiationof that wavelength and the radiation passes through a sample containingboth the analyte and the interferent, both the analyte and theinterferent absorb the radiation. The total absorption reading of thedetector is thus fully attributable to neither the analyte nor theinterferent, but a combination of the two. However, if data existsrelating to how much radiation of a given wavelength is absorbed by agiven interferent when the radiation passes through a sample with agiven pathlength, the contribution of the interferent can be subtractedfrom the total reading of the detector and the remaining value canprovide information regarding concentration of the analyte in thesample. A similar approach can be taken for a whole spectrum ofwavelengths. If data exists relating to how much radiation is absorbedby an interferent over a range of wavelengths when the radiation passesthrough a sample with a given pathlength, the interferent absorbancespectrum can be subtracted from the total absorbance spectrum, leavingonly the analyte's absorbance spectrum for that range of wavelengths. Ifthe interferent absorption data is taken for a range of possiblepathlengths, it can be helpful to determine the pathlength of aparticular sample chamber first so that the correct data can be foundfor samples measured in that sample chamber.

This same process can be applied iteratively or simultaneously formultiple interferents and/or multiple analytes. For example, the waterabsorbance spectrum and the protein absorbance spectrum can both besubtracted to leave behind the glucose absorbance spectrum.

The pathlength can also be calculated using an isosbestic wavelength. Anisosbestic wavelength is one at which all components of a sample havethe same absorbance. If the components (and their absorptioncoefficients) in a particular sample are known, and one or multipleisosbestic wavelengths are known for those particular components, theabsorption data collected by the radiation detector at those isosbesticwavelengths can be used to calculate the pathlength. This can beadvantageous because the needed information can be obtained frommultiple readings of the absorption detector that are taken atapproximately the same time, with the same sample in place in the samplechamber. The isosbestic wavelength readings are used to determinepathlength, and other selected wavelength readings are used to determineinterferent and/or analyte concentration. Thus, this approach isefficient and does not require insertion of a reference fluid in thesample chamber.

In some embodiments, a method of determining concentration of an analytein a sample can include inserting a fluid sample into a samplecontainer, emitting radiation from a source through the container andthe fluid sample, obtaining total sample absorbance data by measuringthe amount of radiation that reaches the detector, subtracting thecorrect interferent absorbance value or spectrum from the total sampleabsorbance data, and using the remaining absorbance value or spectrum todetermine concentration of an analyte in the fluid sample. The correctinterferent absorbance value can be determined using the calculatedpathlength.

The concentration of an analyte in a sample can be calculated using theBeer-Lambert law (or Beer's Law) as follows: If T is transmittance, A isabsorbance, P₀ is initial radiant power directed toward a sample, and Pis the power that emerges from the sample and reaches a detector, thenT=P/P₀, and A=−log T=log (P₀/P). Absorbance is directly proportional tothe concentration (c) of the light-absorbing species in the sample, alsoknown as an analyte or an interferent. Thus, if e is the molarabsorptivity (1/M 1/cm), b is the path length (cm), and c is theconcentration (M), Beer's Law can be expressed as follows: A=e b c.Thus, c=A/(e b).

Referring once again to flowchart 3100, the next step is to determinewhich Library Interferents are present in the sample. In particular,Block 3120 indicates that the measurements are analyzed to identifypossible interferents. For spectroscopic measurements, it is preferredthat the determination is made by comparing the obtained measurement tointerferent spectra in the optical density domain. The results of thisstep provide a list of interferents that may, or are likely to, bepresent in the sample. In one embodiment, several input parameters areused to estimate a glucose concentration g_(est) from a measuredspectrum, C_(s). The input parameters include previously gatheredspectrum measurement of samples that, like the measurement sample,include the analyte and combinations of possible interferents from theinterferent library; and spectrum and concentration ranges for eachpossible interferent. More specifically, the input parameters are:

-   -   Library of Interferent Data: Library of Interferent Data        includes, for each of “M” interferents, the absorption spectrum        of each interferent, IF={IF₁, IF₂, . . . , IF_(M)}, where m=1,        2, . . . , M; and a maximum concentration for each interferent,        Tmax={Tmax₁, Tmax₂, . . . , Tmax_(M)}; and    -   Sample Population Data: Sample Population Data includes        individual spectra of a statistically large population taken        over the same wavelength range as the sample spectrum, Cs_(i),        and an analyte concentration corresponding to each spectrum. As        an example, if there are N Sample Population spectra, then the        spectra can be represented as C={C₁, C₂, . . . , C_(N)}, where        n=1, 2, . . . , N, and the analyte concentration corresponding        to each spectrum can be represented as g={g₁, g₂, . . . ,        g_(N)}.

Preferably, the Sample Population does not have any of the Minterferents present, and the material sample has interferents containedin the Sample Population and none or more of the Library Interferents.Stated in terms of Type-A and Type-B interferents, the Sample Populationhas Type-A interferents and the material sample has Type-A and may haveType-B interferents. The Sample Population Data are used tostatistically quantify an expected range of spectra and analyteconcentrations. Thus, for example, for a system 10 or 334 used todetermine glucose in blood of a person having unknown spectralcharacteristics, the spectral measurements are preferably obtained froma statistical sample of the population.

The following discussion illustrates embodiments for measuring more thanone analyte using spectroscopic techniques. If two or more analytes havenon-overlapping spectral features, then a first embodiment is to obtaina spectrum corresponding to each analyte. The measurements may then beanalyzed for each analyte according to the method of flowchart 4900 asindicated by arrow 4901. An alternative embodiment for analytes havingnon-overlapping features, or an embodiment for analytes havingoverlapping features, is to make one measurement comprising the spectralfeatures of the two or more analytes. The measurement may then beanalyzed for each analyte according to the method of flowchart 4900 asindicated by arrow 4903. That is, the measurement is analyzed for eachanalyte, with the other analytes considered to be interferents to theanalyte being analyzed for.

The following discussion, which is not meant to limit the scope of thepresent disclosure, illustrates embodiments for measuring more than oneanalyte using spectroscopic techniques. If two or more analytes havenon-overlapping spectral features, then a first embodiment is to obtaina spectrum corresponding to each analyte. The measurements may then beanalyzed for each analyte according to the method of flowchart 3100. Analternative embodiment for analytes having non-overlapping features, oran embodiment for analytes having overlapping features, is to make onemeasurement comprising the spectral features of the two or moreanalytes. The measurement may then be analyzed for each analyteaccording to the method of flowchart 3100. That is, the measurement isanalyzed for each analyte, with the other analytes considered to beinterferents to the analyte being analyzed for.

Interferent Determination

One embodiment of the method of Block 3120 is shown in greater detailwith reference to the flowchart of FIG. 32. The method includes forminga statistical Sample Population model (Block 3210), assembling a libraryof interferent data (Block 3220), comparing the obtained measurement andstatistical Sample Population model with data for each interferent froman interferent library (Block 3230), performing a statistical test forthe presence of each interferent from the interferent library (Block3240), and identifying each interferent passing the statistical test asa possible Library Interferent (Block 3250). The steps of Block 3220 canbe performed once or can be updated as necessary. The steps of Blocks3230, 3240, and 3250 can either be performed sequentially for allinterferents of the library, as shown, or alternatively, be repeatedsequentially for each interferent.

One embodiment of each of the methods of Blocks 3210, 3220, 3230, 3240,and 3250 are now described for the example of identifying LibraryInterferents in a sample from a spectroscopic measurement using SamplePopulation Data and a Library of Interferent Data, as discussedpreviously. Each Sample Population spectrum includes measurements (e.g.,of optical density) taken on a sample in the absence of any LibraryInterferents and has an associated known analyte concentration. Astatistical Sample Population model is formed (Block 3210) for the rangeof analyte concentrations by combining all Sample Population spectra toobtain a mean matrix and a covariance matrix for the Sample Population.Thus, for example, if each spectrum at n different wavelengths isrepresented by an n×1 matrix, C, then the mean spectrum, μ, is a n×1matrix with the (e.g., optical density) value at each wavelengthaveraged over the range of spectra, and the covariance matrix, V, is theexpected value of the deviation between C and μ as V=E((C−μ) (C−μ)^(T)).The matrices μ and V are one model that describes the statisticaldistribution of the Sample Population spectra.

In another step, Library Interferent information is assembled (Block3220). A number of possible interferents are identified, for example asa list of possible medications or foods that might be ingested by thepopulation of patients at issue or measured by system 10 or 334, andtheir spectra (in the absorbance, optical density, or transmissiondomains) are obtained. In addition, a range of expected interferentconcentrations in the blood, or other expected sample material, areestimated. Thus, each of M interferents has spectrum IF and maximumconcentration Tmax. This information is preferably assembled once and isaccessed as needed.

The obtained measurement data and statistical Sample Population modelare next compared with data for each interferent from the interferentlibrary (Block 3230) to perform a statistical test (Block 3240) todetermine the identity of any interferent in the mixture (Block 3250).This interferent test will first be shown in a rigorous mathematicalformulation, followed by a discussion of FIGS. 33A and 33B whichillustrates the method.

Mathematically, the test of the presence of an interferent in ameasurement proceeds as follows. The measured optical density spectrum,C_(s), is modified for each interferent of the library by analyticallysubtracting the effect of the interferent, if present, on the measuredspectrum. More specifically, the measured optical density spectrum,C_(s), is modified, wavelength-by-wavelength, by subtracting aninterferent optical density spectrum. For an interferent, M, having anabsorption spectrum per unit of interferent concentration, IF_(M), amodified spectrum is given by C′_(s)(T)=C_(s)−IF_(M) T, where T is theinterferent concentration, which ranges from a minimum value, Tmin, to amaximum value Tmax. The value of Tmin may be zero or, alternatively, bea value between zero and Tmax, such as some fraction of Tmax.

Next, the Mahalanobis distance (MD) between the modified spectrum C′_(s)(T) and the statistical model (μ, V) of the Sample Population spectra iscalculated as:MD ²(C _(s)−(T t),μ; ρ_(δ))=(C _(s)−(T IF _(m))−μ)^(T) V ⁻¹(C _(s)−(T IF_(m))−μ)  Eq. (1)

The test for the presence of interferent IF is to vary T from Tmin toTmax (i.e., evaluate C'_(s) (T) over a range of values of T) anddetermine whether the minimum MD in this interval is in a predeterminedrange. Thus for example, one could determine whether the minimum MD inthe interval is sufficiently small relative to the quantiles of a χ²random variable with L degrees of freedom (L=number of wavelengths).

FIG. 33A is a graph 3300 illustrating the steps of Blocks 3230 and 3240.The axes of graph 3300, OD_(i) and OD_(j), are used to plot opticaldensities at two of the many wavelengths at which measurements areobtained. The points 3301 are the measurements in the Sample Populationdistribution. Points 3301 are clustered within an ellipse that has beendrawn to encircle the majority of points. Points 3301 inside ellipse3302 represent measurements in the absence of Library Interferents.Point 3303 is the sample measurement. Presumably, point 3303 is outsideof the spread of points 3301 due the presence of one or more LibraryInterferents. Lines 3304, 3307, and 3309 indicate the measurement ofpoint 3303 as corrected for increasing concentration, T, of threedifferent Library Interferents over the range from Tmin to Tmax. Thethree interferents of this example are referred to as interferent #1,interferent #2, and interferent #3. Specifically, lines 3304, 3307, and3309 are obtained by subtracting from the sample measurement an amount Tof a Library Interferent (interferent #1, interferent #2, andinterferent #3, respectively), and plotting the corrected samplemeasurement for increasing T.

FIG. 33B is a graph further illustrating the method of FIG. 32. In thegraph of FIG. 33B, the squared Mahalanobis distance, MD² has beencalculated and plotted as a function of t for lines 3304, 3307, and3309. Referring to FIG. 33A, line 3304 reflects decreasingconcentrations of interferent #1 and only slightly approaches points3301. The value of MD² of line 3304, as shown in FIG. 33B, decreasesslightly and then increases with decreasing interferent #1concentration.

Referring to FIG. 33A, line 3307 reflects decreasing concentrations ofinterferent #2 and approaches or passes through many points 3301. Thevalue of MD² of line 3307, as shown in FIG. 33B, shows a large decreaseat some interferent #2 concentration, then increases. Referring to FIG.33A, line 3309 has decreasing concentrations of interferent #3 andapproaches or passes through even more points 3303. The value of MD² ofline 3309, as shown in FIG. 33B, shows a still larger decrease at someinterferent #3 concentration.

In one embodiment, a threshold level of MD² is set as an indication ofthe presence of a particular interferent. Thus, for example, FIG. 33Bshows a line labeled “original spectrum” indicating MD² when nointerferents are subtracted from the spectrum, and a line labeled “95%Threshold”, indicating the 95% quantile for the chi² distribution with Ldegrees of freedom (where L is the number of wavelengths represented inthe spectra). This level is the value which should exceed 95% of thevalues of the MD² metric; in other words, values at this level areuncommon, and those far above it should be quite rare. Of the threeinterferents represented in FIGS. 33A and 33B, only interferent #3 has avalue of MD² below the threshold. Thus, this analysis of the sampleindicates that interferent #3 is the most likely interferent present inthe sample. Interferent #1 has its minimum far above the threshold leveland is extremely unlikely to be present; interferent #2 barely crossesthe threshold, making its presence more likely than interferent #1, butstill far less likely to be present than interferent #1.

As described subsequently, information related to the identifiedinterferents is used in generating a calibration constant that isrelatively insensitive to a likely range of concentration of theidentified interferents. In addition to being used in certain methodsdescribed subsequently, the identification of the interferents may be ofinterest and may be provided in a manner that would be useful. Thus, forexample, for a hospital based glucose monitor, identified interferentsmay be reported on display 141 or be transmitted to a hospital computervia communications link 216.

Calibration Constant Generation Embodiments

Once Library Interferents are identified as being possibly present inthe sample under analysis, a calibration constant for estimating theconcentration of analytes in the presence of the identified interferentsis generated (Block 3130). More specifically, after Block 3120, a listof possible Library Interferents is identified as being present. Oneembodiment of the steps of Block 3120 are shown in the flowchart of FIG.34 as Block 3410, where synthesized Sample Population measurements aregenerated, Block 3420, where the synthesized Sample Populationmeasurements are partitioned in to calibration and test sets, Block3430, where the calibration are is used to generate a calibrationconstant, Block 3440, where the calibration set is used to estimate theanalyte concentration of the test set, Block 3450 where the errors inthe estimated analyte concentration of the test set is calculated, andBlock 3460 where an average calibration constant is calculated.

One embodiment of each of the methods of Blocks 3410, 3420, 3430, 3440,3450, and 3460 are now described for the example of using identifyinginterferents in a sample for generating an average calibration constant.As indicated in Block 3410, one step is to generate synthesized SamplePopulation spectra, by adding a random concentration of possible LibraryInterferents to each Sample Population spectrum. The spectra generatedby the method of Block 3410 are referred to herein as anInterferent-Enhanced Spectral Database, or IESD. The IESD can be formedby the steps illustrated in FIGS. 35-38, where FIG. 35 is a schematicdiagram 3500 illustrating the generation of Randomly-Scaled SingleInterferent Spectra, or RSIS; FIG. 36 is a graph 3600 of the interferentscaling; FIG. 37 is a schematic diagram illustrating the combination ofRSIS into Combination Interferent Spectra, or CIS; and FIG. 38 is aschematic diagram illustrating the combination of CIS and the SamplePopulation spectra into an IESD.

The first step in Block 3410 is shown in FIGS. 35 and 36. As shownschematically in flowchart 3500 in FIG. 35, and in graph 3600 in FIG.36, a plurality of RSIS (Block 3540) are formed by combinations of eachpreviously identified Library Interferent having spectrum IF_(m) (Block3510), multiplied by the maximum concentration Tmax_(m) (Block 3520)that is scaled by a random factor between zero and one (Block 3530), asindicated by the distribution of the random number indicated in graph3600. In one embodiment, the scaling places the maximum concentration atthe 95^(th) percentile of a log-normal distribution to produce a widerange of concentrations with the distribution having a standarddeviation equal to half of its mean value. The distribution of therandom numbers in graph 3600 are a log-normal distribution of μ=100,σ=50.

Once the individual Library Interferent spectra have been multiplied bythe random concentrations to produce the RSIS, the RSIS are combined toproduce a large population of interferent-only spectra, the CIS, asillustrated in FIG. 37. The individual RSIS are combined independentlyand in random combinations, to produce a large family of CIS, with eachspectrum within the CIS consisting of a random combination of RSIS,selected from the full set of identified Library Interferents. Themethod illustrated in FIG. 37 produces adequate variability with respectto each interferent, independently across separate interferents.

The next step combines the CIS and replicates of the Sample Populationspectra to form the IESD, as illustrated in FIG. 38. Since theInterferent Data and Sample Population spectra may have been obtained atdifferent pathlengths, the CIS are first scaled (i.e., multiplied) tothe same pathlength. The Sample Population database is then replicated Mtimes, where M depends on the size of the database, as well as thenumber of interferents to be treated. The IESD includes M copies of eachof the Sample Population spectra, where one copy is the original SamplePopulation Data, and the remaining M−1 copies each have an added randomone of the CIS spectra. Each of the IESD spectra has an associatedanalyte concentration from the Sample Population spectra used to formthe particular IESD spectrum.

In one embodiment, a 10-fold replication of the Sample Populationdatabase is used for 130 Sample Population spectra obtained from 58different individuals and 18 Library Interferents. Greater spectralvariety among the Library Interferent spectra requires a smallerreplication factor, and a greater number of Library Interferentsrequires a larger replication factor.

The steps of Blocks 3420, 3430, 3440, and 3450 are executed torepeatedly combine different ones of the spectra of the IESD tostatistically average out the effect of the identified LibraryInterferents. First, as noted in Block 3420, the IESD is partitionedinto two subsets: a calibration set and a test set. As describedsubsequently, the repeated partitioning of the IESD into differentcalibration and test sets improves the statistical significance of thecalibration constant. In one embodiment, the calibration set is a randomselection of some of the IESD spectra and the test set are theunselected IESD spectra. In a preferred embodiment, the calibration setincludes approximately two-thirds of the IESD spectra.

In an alternative embodiment, the steps of Blocks 3420, 3430, 3440, and3450 are replaced with a single calculation of an average calibrationconstant using all available data.

Next, as indicted in Block 3430, the calibration set is used to generatea calibration constant for predicting the analyte concentration from asample measurement. First an analyte spectrum is obtained. For theembodiment of glucose determined from absorption measurements, a glucoseabsorption spectrum is indicated as α_(G). The calibration constant isthen generated as follows. Using the calibration set having calibrationspectra C={c₁, c₂, . . . , c_(n)} and corresponding glucoseconcentration values G={g₁, g₂, . . . g_(n)}, then glucose-free spectraC′={c′₁, c′₂, . . . , c′_(n)} can be calculated as: c′_(j)=c_(j)−α_(G)g_(j). Next, the calibration constant, κ, is calculated from C′ andα_(G), according to the following 5 steps:

-   -   1) C′ is decomposed into C′=A_(c′)Δ_(c′)B_(c′), that is, a        singular value decomposition, where the A-factor is an        orthonormal basis of column space, or span, of C′;    -   2) A_(c′) is truncated to avoid overfitting to a particular        column rank r, based on the sizes of the diagonal entries of Δ        (the singular values of C′). The selection of r involves a        trade-off between the precision and stability of the        calibration, with a larger r resulting in a more precise but        less stable solution. In one embodiment, each spectrum C        includes 25 wavelengths, and r ranges from 15 to 19;    -   3) The first r columns of A_(c′) are taken as an orthonormal        basis of span(C′);    -   4) The projection from the background is found as the product        P_(c′)=A_(c′)A_(c′) ^(T), that is the orthogonal projection onto        the span of C′, and the complementary, or nulling projection        P_(C′) ^(⊥)=1−P_(c′), which forms the projection onto the        complementary subspace C′^(⊥), is calculated; and    -   5) The calibration vector κ is then found by applying the        nulling projection to the absorption spectrum of the analyte of        interest: κ_(RAW)=P_(c′) ^(⊥)α_(G), and normalizing:        κ=κ_(RAW)/<κ_(RAW), α_(G)>, where the angle brackets <,> denote        the standard inner (or dot) product of vectors. The normalized        calibration constant produces a unit response for a unit α_(G)        spectral input for one particular calibration set.

Next, the calibration constant is used to estimate the analyteconcentration in the test set (Block 3440). Specifically, each spectrumof the test set (each spectrum having an associated glucoseconcentration from the Sample Population spectra used to generate thetest set) is multiplied by the calibration vector κ from Block 3430 tocalculate an estimated glucose concentration. The error between thecalculated and known glucose concentration is then calculated (Block3450). Specifically, the measure of the error can include a weightedvalue averaged over the entire test set according to 1/rms².

Blocks 3420, 3430, 3440, and 3450 are repeated for many different randomcombinations of calibration sets. Preferably, Blocks 3420, 3430, 3440,and 3450 are repeated are repeated hundreds to thousands of times.Finally, an average calibration constant is calculated from thecalibration and error from the many calibration and test sets (Block3460). Specifically, the average calibration is computed as weightedaverage calibration vector. In one embodiment the weighting is inproportion to a normalized rms, such as the κ_(ave)=κ*rms²/Σ(rms²) forall tests.

With the last of Block 3130 executed according to FIG. 34, the averagecalibration constant κ_(ave) is applied to the obtained spectrum (Block3140).

Accordingly, one embodiment of a method of computing a calibrationconstant based on identified interferents can be summarized as follows:

-   -   1. Generate synthesized Sample Population spectra by adding the        RSIS to raw (interferent-free) Sample Population spectra, thus        forming an Interferent Enhanced Spectral Database (IESD)—each        spectrum of the IESD is synthesized from one spectrum of the        Sample Population, and thus each spectrum of the IESD has at        least one associated known analyte concentration    -   2. Separate the spectra of the IESD into a calibration set of        spectra and a test set of spectra    -   3. Generate a calibration constant for the calibration set based        on the calibration set spectra and their associated known        correct analyte concentrations (e.g., using the matrix        manipulation outlined in five steps above)    -   4. Use the calibration constant generated in step 3 to calculate        the error in the corresponding test set as follows (repeat for        each spectrum in the test set):        -   a. Multiply (the selected test set spectrum)×(average            calibration constant generated in step 3) to generate an            estimated glucose concentration        -   b. Evaluate the difference between this estimated glucose            concentration and the known, correct glucose concentration            associated with the selected test spectrum to generate an            error associated with the selected test spectrum    -   5. Average the errors calculated in step 4 to arrive at a        weighted or average error for the current calibration set—test        set pair    -   6. Repeat steps 2 through 5 n times, resulting in n calibration        constants and n average errors    -   7. Compute a “grand average” error from the n average errors and        an average calibration constant from the n calibration constants        (preferably weighted averages wherein the largest average errors        and calibration constants are discounted), to arrive at a        calibration constant which is minimally sensitive to the effect        of the identified interferents

EXAMPLE 1

One example of certain methods disclosed herein is illustrated withreference to the detection of glucose in blood using mid-IR absorptionspectroscopy. Table 2 lists 10 Library Interferents (each havingabsorption features that overlap with glucose) and the correspondingmaximum concentration of each Library Interferent. Table 2 also lists aGlucose Sensitivity to Interferent without and with training. TheGlucose Sensitivity to Interferent is the calculated change in estimatedglucose concentration for a unit change in interferent concentration.For a highly glucose selective analyte detection technique, this valueis zero. The Glucose Sensitivity to Interferent without training is theGlucose Sensitivity to Interferent where the calibration has beendetermined using the methods above without any identified interferents.The Glucose Sensitivity to Interferent with training is the GlucoseSensitivity to Interferent where the calibration has been determinedusing the methods above with the appropriately identified interferents.In this case, least improvement (in terms of reduction in sensitivity toan interferent) occurs for urea, seeing a factor of 6.4 lowersensitivity, followed by three with ratios from 60 to 80 in improvement.The remaining six all have seen sensitivity factors reduced by over 100,up to over 1600. The decreased Glucose Sensitivity to Interferent withtraining indicates that the methods are effective at producing acalibration constant that is selective to glucose in the presence ofinterferents.

TABLE 2 Rejection of 10 interfering substances Glucose GlucoseSensitivity to Sensitivity to Library Maximum Interferent InterferentInterferent Concentration w/o training w/training Sodium Bicarbonate 1030.330 0.0002 Urea 100 −0.132 0.0206 Magnesium Sulfate 0.7 1.056 −0.0016Naproxen 10 0.600 −0.0091 Uric Acid 12 −0.557 0.0108 Salicylate 10 0.411−0.0050 Glutathione 100 0.041 0.0003 Niacin 1.8 1.594 −0.0086Nicotinamide 12.2 0.452 −0.0026 Chlorpropamide 18.3 0.334 0.0012

EXAMPLE 2

Another example illustrates the effect of the methods for 18interferents. Table 3 lists of 18 interferents and maximumconcentrations that were modeled for this example, and the glucosesensitivity to the interferent without and with training. The tablesummarizes the results of a series of 1000 calibration and testsimulations that were performed both in the absence of the interferents,and with all interferents present. FIG. 39 shows the distribution of theR.M.S. error in the glucose concentration estimation for 1000 trials.While a number of substances show significantly less sensitivity (sodiumbicarbonate, magnesium sulfate, tolbutamide), others show increasedsensitivity (ethanol, acetoacetate), as listed in Table 3. The curves inFIG. 39 are for calibration set and the test set both without anyinterferents and with all 18 interferents. The interferent produces adegradation of performance, as can be seen by comparing the calibrationor test curves of FIG. 39. Thus, for example, the peaks appear to beshifted by about 2 mg/dL, and the width of the distributions isincreased slightly. The reduction in height of the peaks is due to thespreading of the distributions, resulting in a modest degradation inperformance.

TABLE 3 List of 18 Interfering Substances with maximum concentrationsand Sensitivity with respect to interferents, with/without trainingGlucose Glucose Sensitivity Sensitivity to Library Conc. to Interferentw/o Interferent w/ Interferent (mg/dL) training training 1 Urea 300−0.167 −0.100 2 Ethanol 400.15 −0.007 −0.044 3 Sodium Bicarbonate 4890.157 −0.093 4 Acetoacetate Li 96 0.387 0.601 5 Hydroxybutyric Acid 465−0.252 −0.101 6 Magnesium Sulfate 29.1 2.479 0.023 7 Naproxen 49.910.442 0.564 8 Salicylate 59.94 0.252 0.283 9 Ticarcillin Disodium 102−0.038 −0.086 10 Cefazolin 119.99 −0.087 −0.006 11 Chlorpropamide 27.70.387 0.231 12 Nicotinamide 36.6 0.265 0.366 13 Uric Acid 36 −0.641−0.712 14 Ibuprofen 49.96 −0.172 −0.125 15 Tolbutamide 63.99 0.132 0.00416 Tolazamide 9.9 0.196 0.091 17 Bilirubin 3 −0.391 −0.266 18Acetaminophen 25.07 0.169 0.126

EXAMPLE 3

In a third example, certain methods disclosed herein were tested formeasuring glucose in blood using mid-IR absorption spectroscopy in thepresence of four interferents not normally found in blood (Type-Binterferents) and that may be common for patients in hospital intensivecare units (ICUs). The four Type-B interferents are mannitol, dextran,n-acetyl L cysteine, and procainamide.

Of the four Type-B interferents, mannitol and dextran have the potentialto interfere substantially with the estimation of glucose: both arespectrally similar to glucose (see FIG. 1), and the dosages employed inICUs are very large in comparison to typical glucose levels. Mannitol,for example, may be present in the blood at concentrations of 2500mg/dL, and dextran may be present at concentrations in excess of 5000mg/dL. For comparison, typical plasma glucose levels are on the order of100-200 mg/dL. The other Type-B interferents, n-acetyl L cysteine andprocainamide, have spectra that are quite unlike the glucose spectrum.

FIGS. 40A, 40B, 40C, and 40D each have a graph showing a comparison ofthe absorption spectrum of glucose with different interferents takenusing two different techniques: a Fourier Transform Infrared (FTIR)spectrometer having an interpolated resolution of 1 cm⁻¹ (solid lineswith triangles); and by 25 finite-bandwidth IR filters having a Gaussianprofile and full-width half-maximum (FWHM) bandwidth of 28 cm⁻¹corresponding to a bandwidth that varies from 140 nm at 7.08 μm, up to279 nm at 10 μm (dashed lines with circles). Specifically, the figuresshow a comparison of glucose with mannitol (FIG. 40A), with dextran(FIG. 40B), with n-acetyl L cysteine (FIG. 40C), and with procainamide(FIG. 40D), at a concentration level of 1 mg/dL and path length of 1 μm.The horizontal axis in FIGS. 40A-40D has units of wavelength in microns(μm), ranging from 7 μm to 10 μm, and the vertical axis has arbitraryunits.

The central wavelength of the data obtained using filter is indicated inFIGS. 40A, 40B, 40C, and 40D by the circles along each dashed curve, andcorresponds to the following wavelengths, in microns: 7.082, 7.158,7.241, 7.331, 7.424, 7.513, 7.605, 7.704, 7.800, 7.905, 8.019, 8.150,8.271, 8.598, 8.718, 8.834, 8.969, 9.099, 9.217, 9.346, 9.461, 9.579,9.718, 9.862, and 9.990. The effect of the bandwidth of the filters onthe spectral features can be seen in FIGS. 40A-40D as the decrease inthe sharpness of spectral features on the solid curves and the relativeabsence of sharp features on the dashed curves.

FIG. 41 shows a graph of the blood plasma spectra for 6 blood samplesthree donors in arbitrary units for a wavelength range from 7 μm to 10μm, where the symbols on the curves indicate the central wavelengths ofthe 25 filters. The 6 blood samples do not contain any mannitol,dextran, n-acetyl L cysteine, and procainamide—the Type-B interferentsof this Example, and are thus a Sample Population. Three donors(indicated as donar A, B, and C) provided blood at different times,resulting in different blood glucose levels, shown in the graph legendin mg/dL as measured using a YSI Biochemistry Analyzer (YSIIncorporated, Yellow Springs, Ohio). The path length of these samples,estimated at 36.3 μm by analysis of the spectrum of a reference scan ofsaline in the same cell immediately prior to each sample spectrum, wasused to normalize these measurements. This quantity was taken intoaccount in the computation of the calibration vectors provided, and theapplication of these vectors to spectra obtained from other equipmentwould require a similar pathlength estimation and normalization processto obtain valid results.

Next, random amounts of each Type-B interferent of this Example areadded to the spectra to produce mixtures that, for example could make upan Interferent Enhanced Spectral. Each of the Sample Population spectrawas combined with a random amount of a single interferent added, asindicated in Table 4, which lists an index number N, the Donor, theglucose concentration (GLU), interferent concentration (conc(IF)), andthe interferent for each of 54 spectra. The conditions of Table 4 wereused to form combined spectra including each of the 6 plasma spectra wascombined with 2 levels of each of the 4 interferents.

TABLE 4 Interferent Enhanced Spectral Database for Example 3. N DonorGLU conc(IF) IF 1 A 157.7 N/A 2 A 382 N/A 3 B 122 N/A 4 B 477.3 N/A 5 C199.7 N/A 6 C 399 N/A 7 A 157.7 1001.2 Mannitol 8 A 382 2716.5 Mannitol9 A 157.7 1107.7 Mannitol 10 A 382 1394.2 Mannitol 11 B 122 2280.6Mannitol 12 B 477.3 1669.3 Mannitol 13 B 122 1710.2 Mannitol 14 B 477.31113.0 Mannitol 15 C 199.7 1316.4 Mannitol 16 C 399 399.1 Mannitol 17 C199.7 969.8 Mannitol 18 C 399 2607.7 Mannitol 19 A 157.7 8.8 N Acetyl LCysteine 20 A 382 2.3 N Acetyl L Cysteine 21 A 157.7 3.7 N Acetyl LCysteine 22 A 382 8.0 N Acetyl L Cysteine 23 B 122 3.0 N Acetyl LCysteine 24 B 477.3 4.3 N Acetyl L Cysteine 25 B 122 8.4 N Acetyl LCysteine 26 B 477.3 5.8 N Acetyl L Cysteine 27 C 199.7 7.1 N Acetyl LCysteine 28 C 399 8.5 N Acetyl L Cysteine 29 C 199.7 4.4 N Acetyl LCysteine 30 C 399 4.3 N Acetyl L Cysteine 31 A 157.7 4089.2 Dextran 32 A382 1023.7 Dextran 33 A 157.7 1171.8 Dextran 34 A 382 4436.9 Dextran 35B 122 2050.6 Dextran 36 B 477.3 2093.3 Dextran 37 B 122 2183.3 Dextran38 B 477.3 3750.4 Dextran 39 C 199.7 2598.1 Dextran 40 C 399 2226.3Dextran 41 C 199.7 2793.0 Dextran 42 C 399 2941.8 Dextran 43 A 157.722.5 Procainamide 44 A 382 35.3 Procainamide 45 A 157.7 5.5 Procainamide46 A 382 7.7 Procainamide 47 B 122 18.5 Procainamide 48 B 477.3 5.6Procainamide 49 B 122 31.8 Procainamide 50 B 477.3 8.2 Procainamide 51 C199.7 22.0 Procainamide 52 C 399 9.3 Procainamide 53 C 199.7 19.7Procainamide 54 C 399 12.5 Procainamide

FIGS. 42A, 42B, 42C, and 42D contain spectra formed from the conditionsof Table 4. Specifically, the figures show spectra of the SamplePopulation of 6 samples having random amounts of mannitol (FIG. 42A),dextran (FIG. 42B), n-acetyl L cysteine (FIG. 42C), and procainamide(FIG. 42D), at a concentration levels of 1 mg/dL and path lengths of 1μm.

Next, calibration vectors were generated using the spectra of FIGS.42A-42D, in effect reproducing the steps of Block 3120. The next step ofthis Example is the spectral subtraction of water that is present in thesample to produce water-free spectra. As discussed above, certainmethods disclosed herein provide for the estimation of an analyteconcentration in the presence of interferents that are present in both asample population and the measurement sample (Type-A interferents), andit is not necessary to remove the spectra for interferents present inSample Population and sample being measured. The step of removing waterfrom the spectrum is thus an alternative embodiment of the disclosedmethods.

The calibration vectors are shown in FIGS. 43A-43D for mannitol (FIG.43A), dextran (FIG. 43B), n-acetyl L cysteine (FIG. 43C), andprocainamide (FIG. 43D) for water-free spectra. Specifically each one ofFIGS. 43A-43D compares calibration vectors obtained by training in thepresence of an interferent, to the calibration vector obtained bytraining on clean plasma spectra alone. The calibration vector is usedby computing its dot-product with the vector representing(pathlength-normalized) spectral absorption values for the filters usedin processing the reference spectra. Large values (whether positive ornegative) typically represent wavelengths for which the correspondingspectral absorbance is sensitive to the presence of glucose, while smallvalues generally represent wavelengths for which the spectral absorbanceis insensitive to the presence of glucose. In the presence of aninterfering substance, this correspondence is somewhat less transparent,being modified by the tendency of interfering substances to mask thepresence of glucose.

The similarity of the calibration vectors obtained for minimizing theeffects of the two interferents n-acetyl L cysteine and procainamide, tothat obtained for pure plasma, is a reflection of the fact that thesetwo interferents are spectrally quite distinct from the glucosespectrum; the large differences seen between the calibration vectors forminimizing the effects of dextran and mannitol, and the calibrationobtained for pure plasma, are conversely representative of the largedegree of similarity between the spectra of these substances and that ofglucose. For those cases in which the interfering spectrum is similar tothe glucose spectrum (that is, mannitol and dextran), the greatestchange in the calibration vector. For those cases in which theinterfering spectrum is different from the glucose spectrum (that is,n-acetyl L cysteine and procainamide), it is difficult to detect thedifference between the calibration vectors obtained with and without theinterferent.

It will be understood that the steps of methods discussed are performedin one embodiment by an appropriate processor (or processors) of aprocessing (i.e., computer) system executing instructions (codesegments) stored in appropriate storage. It will also be understood thatthe disclosed methods and apparatus are not limited to any particularimplementation or programming technique and that the methods andapparatus may be implemented using any appropriate techniques forimplementing the functionality described herein. The methods andapparatus are not limited to any particular programming language oroperating system. In addition, the various components of the apparatusmay be included in a single housing or in multiple housings thatcommunication by wire or wireless communication.

Further, the interferent, analyte, or population data used in the methodmay be updated, changed, added, removed, or otherwise modified asneeded. Thus, for example, spectral information and/or concentrations ofinterferents that are accessible to the methods may be updated orchanged by updating or changing a database of a program implementing themethod. The updating may occur by providing new computer readable mediaor over a computer network. Other changes that may be made to themethods or apparatus include, but are not limited to, the adding ofadditional analytes or the changing of population spectral information.

One embodiment of each of the methods described herein may include acomputer program accessible to and/or executable by a processing system,e.g., a one or more processors and memories that are part of an embeddedsystem. Thus, as will be appreciated by those skilled in the art,embodiments of the disclosed inventions may be embodied as a method, anapparatus such as a special purpose apparatus, an apparatus such as adata processing system, or a carrier medium, e.g., a computer programproduct. The carrier medium carries one or more computer readable codesegments for controlling a processing system to implement a method.Accordingly, various ones of the disclosed inventions may take the formof a method, an entirely hardware embodiment, an entirely softwareembodiment or an embodiment combining software and hardware aspects.Furthermore, any one or more of the disclosed methods (including but notlimited to the disclosed methods of measurement analysis, interferentdetermination, and/or calibration constant generation) may be stored asone or more computer readable code segments or data compilations on acarrier medium. Any suitable computer readable carrier medium may beused including a magnetic storage device such as a diskette or a harddisk; a memory cartridge, module, card or chip (either alone orinstalled within a larger device); or an optical storage device such asa CD or DVD.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, appearances of the phrases “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined inany suitable manner, as would be apparent to one of ordinary skill inthe art from this disclosure, in one or more embodiments.

Similarly, it should be appreciated that in the above description ofembodiments, various features of the inventions are sometimes groupedtogether in a single embodiment, figure, or description thereof for thepurpose of streamlining the disclosure and aiding in the understandingof one or more of the various inventive aspects. This method ofdisclosure, however, is not to be interpreted as reflecting an intentionthat any claim require more features than are expressly recited in thatclaim. Rather, as the following claims reflect, inventive aspects lie ina combination of fewer than all features of any single foregoingdisclosed embodiment. Thus, the claims following the DetailedDescription are hereby expressly incorporated into this DetailedDescription, with each claim standing on its own as a separateembodiment.

Further information on analyte detection systems, sample elements,algorithms and methods for computing analyte concentrations, and otherrelated apparatus and methods can be found in U.S. Patent ApplicationPublication No. 2003/0090649, published May 15, 2003, titledREAGENT-LESS WHOLE BLOOD GLUCOSE METER; U.S. Patent ApplicationPublication No. 2003/0178569, published Sep. 25, 2003, titledPATHLENGTH-INDEPENDENT METHODS FOR OPTICALLY DETERMINING MATERIALCOMPOSITION; U.S. Patent Application Publication No. 2004/0019431,published Jan. 29, 2004, titled METHOD OF DETERMINING AN ANALYTECONCENTRATION IN A SAMPLE FROM AN ABSORPTION SPECTRUM; U.S. PatentApplication Publication No. 2005/0036147, published Feb. 17, 2005,titled METHOD OF DETERMINING ANALYTE CONCENTRATION IN A SAMPLE USINGINFRARED TRANSMISSION DATA; and U.S. Patent Application Publication No.2005/0038357, published on Feb. 17, 2005, titled SAMPLE ELEMENT WITHBARRIER MATERIAL. The entire contents of each of the above-mentionedpublications are hereby incorporated by reference herein and are made apart of this specification.

A number of applications, publications and external documents areincorporated by reference herein. Any conflict or contradiction betweena statement in the bodily text of this specification and a statement inany of the incorporated documents is to be resolved in favor of thestatement in the bodily text.

Although the invention(s) presented herein have been disclosed in thecontext of certain preferred embodiments and examples, it will beunderstood by those skilled in the art that the invention(s) extendbeyond the specifically disclosed embodiments to other alternativeembodiments and/or uses of the invention(s) and obvious modificationsand equivalents thereof. Thus, it is intended that the scope of theinvention(s) herein disclosed should not be limited by the particularembodiments described above, but should be determined only by a fairreading of the claims that follow.

1. An apparatus for analyzing the composition of bodily fluid, theapparatus comprising: a fluid handling network including a patient endconfigured to maintain fluid communication with a bodily fluid in apatient; at least one pump in operative engagement with the fluidhandling network, the at least one pump having a sample draw mode inwhich the pump is operable to draw a sample of the bodily fluid from thepatient through the patient end; a controller configured to operate theat least one pump in the sample draw mode at intervals; a fluid analyzerpositioned to analyze at least a portion of the sample; a processor incommunication with or incorporated into the fluid analyzer; and storedprogram instructions executable by the processor to determine theconcentrations of two or more analytes in the sample, wherein theprogram instructions are configured to cause the fluid analyzer to:subject the at least a portion of the sample to one or more tests;analyze results from the one or more tests to estimate the concentrationof a first analyte; determine whether the results from the one or moretests are sensitive to a second analyte in the sample; and analyze theat least a portion of the sample to estimate the concentration of thesecond analyte, wherein analyzing the at least a portion of the samplecomprises analyzing the same results from the one or more tests when itis determined that the results from spectral features of the secondanalyte overlap spectral features of the first analyte.
 2. The apparatusof claim 1, where said fluid analyzer analyzes the presence of at leastone analyte in whole blood.
 3. The apparatus of claim 1, where saidfluid analyzer analyzes the presence of at least one analyte in bloodplasma.
 4. The apparatus of claim 1, where said fluid analyzer analyzesthe presence of at least one analyte in blood serum.
 5. The apparatus ofclaim 1, where said fluid analyzer includes a spectroscopic analyzer. 6.The apparatus of claim 5, where said spectroscopic analyzer is aninfrared spectroscopic analyzer.
 7. The apparatus of claim 5, where saidspectroscopic analyzer obtains a spectra of said at least a portion ofthe sample, and where said stored program instructions are furtherconfigured to cause the fluid analyzer to determine the presence of atleast one of said two or more analytes from the spectra.
 8. Theapparatus of claim 7, where said spectra includes spectral features ofsaid two or more analytes.
 9. The apparatus of claim 7, where saidspectra includes two or more spectra each including spectral features ofone of said two or more analytes.
 10. The apparatus of claim 1, whereone of said two or more analytes is glucose.
 11. The apparatus of claim1, where at least one of said two or more analytes is a sugar.
 12. Theapparatus of claim 1, where at least one of said two or more analytes isblood urea nitrogen (BUN), hemoglobin, or lactate.
 13. The apparatus ofclaim 1, where said bodily fluid is blood, and where said fluid analyzeraccepts a sample of the bodily fluid from the fluid handling network andobtain a measurement of the hematocrit of the blood.
 14. A method forautomatically analyzing the composition of a bodily fluid in a patient,the method comprising: a) automatically drawing a sample of the bodilyfluid of the patient through a fluid handling network configured tomaintain fluid communication with a bodily fluid in a patient; b)directing at least a portion of the sample to a fluid analyzer connectedto the fluid handling network; c) obtaining a spectral characterizationof at least a portion of the sample in the fluid analyzer; d) analyzingthe spectral characterization to estimate the concentration of a firstanalyte in the sample, the first analyte being apart from anyinterferents to the measurement of the first analyte; e) determiningwhether a second analyte in the sample is associated with spectralfeatures that overlap spectral features associated with the firstanalyte, the second analyte being apart from any interferents to themeasurement of the second analyte; f) analyzing the at least a portionof the sample to estimate the concentration of the second analyte,wherein analyzing the at least a portion of the sample comprisesanalyzing the spectral characterization when spectral features of thesecond analyte overlap spectral features of the first analyte; g)automatically drawing another sample of the bodily fluid of the patientthrough the fluid handling network after an interval has elapsed; and h)repeating steps b)-f) using the newly-drawn sample.
 15. The method ofclaim 14, where said portion includes whole blood, blood plasma, orblood serum.
 16. The method of claim 14, wherein said spectralcharacterization includes an infrared spectrum.
 17. The method of claim14, where said spectral characterization includes spectral features ofthe first analyte and the second analyte.
 18. The method of claim 14,where one of the first analyte and the second analyte is glucose. 19.The method of claim 14, where at least one of the first analyte and thesecond analyte is a sugar.
 20. The method of claim 14, where at leastone of the first analyte and the second analyte is glucose, blood ureanitrogen (BUN), hemoglobin, or lactate.
 21. The method of claim 14,where said bodily fluid is blood, and said method further comprisesobtaining a measurement of the hematocrit of the blood.